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Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States

Published:April 20, 2011DOI:https://doi.org/10.1016/j.ajog.2011.04.024

      Objective

      To examine the association between electronic fetal heart rate monitoring and neonatal and infant mortality, as well as neonatal morbidity.

      Study Design

      We used the United States 2004 linked birth and infant death data. Multivariable log-binomial regression models were fitted to estimate risk ratio for association between electronic fetal heart rate monitoring and mortality, while adjusting for potential confounders.

      Results

      In 2004, 89% of singleton pregnancies had electronic fetal heart rate monitoring. Electronic fetal heart rate monitoring was associated with significantly lower infant mortality (adjusted relative risk, 0.75); this was mainly driven by the lower risk of early neonatal mortality (adjusted relative risk, 0.50). In low-risk pregnancies, electronic fetal heart rate monitoring was associated with decreased risk for Apgar scores <4 at 5 minutes (relative risk, 0.54); in high-risk pregnancies, with decreased risk of neonatal seizures (relative risk, 0.65).

      Conclusion

      In the United States, the use of electronic fetal heart rate monitoring was associated with a substantial decrease in early neonatal mortality and morbidity that lowered infant mortality.

      Key words

      During labor electronic fetal monitoring (EFM) is used to assure well-being because the inexplicable interplay of antenatal complications, inadequate placental perfusion, and intrapartum events can lead to adverse outcomes.
      American College of Obstetricians and Gynecologists
      Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles ACOG practice bulletin no. 106.
      Even uncomplicated pregnancies are monitored for asphyxial injury and intrapartum death.
      • Low J.A.
      • Pickersgill H.
      • Killen H.
      • Derrick E.J.
      The prediction and prevention of intrapartum fetal asphyxia in term pregnancies.
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      • Wood A.M.
      • Pell J.P.
      • Fleming M.
      • Smith G.C.
      Time of birth and risk of neonatal death at term: retrospective cohort study.
      Indeed, EFM during labor is the most common obstetric procedure in the United States.
      American College of Obstetricians and Gynecologists
      Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles ACOG practice bulletin no. 106.
      From 1997 to 2003 in the United States, EFM was used in 84% of the over 27 million births.
      • Ventura S.J.
      • Martin J.A.
      • Curtin S.C.
      • Mathews T.J.
      Births: final data for 1997.
      • Ventura S.J.
      • Martin J.A.
      • Curtin S.C.
      • Mathews T.J.
      • Park M.M.
      Births: final data for 1998.
      • Ventura S.J.
      • Martin J.A.
      • Curtin S.C.
      • Menacker F.
      • Hamilton B.E.
      Births: final data for 1999.
      • Martin J.A.
      • Hamilton B.E.
      • Ventura S.J.
      • Menacker F.
      • Park M.M.
      Births: final data for 2000.
      • Martin J.A.
      • Hamilton B.E.
      • Ventura S.J.
      • Menacker F.
      • Park M.M.
      • Sutton P.D.
      Births: final data for 2001.
      • Martin J.A.
      • Hamilton B.E.
      • Sutton P.D.
      • Ventura S.J.
      • Menacker F.
      • Munson M.L.
      Births: final data for 2002.
      • Martin J.A.
      • Hamilton B.E.
      • Sutton P.D.
      • et al.
      Births: final data for 2003.
      See related editorial, page 455
      For Editors' Commentary, see Table of Contents
      Despite the ubiquitous use, there are concerns about the efficacy of EFM. As noted by the American College of Obstetricians and Gynecologists (ACOG) practice bulletin,
      American College of Obstetricians and Gynecologists
      Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles ACOG practice bulletin no. 106.
      the efficacy of monitoring is adjudicated by comparing the neonatal morbidity, including seizure and cerebral palsy, or mortality averted vs the unnecessary interventions (operative vaginal or cesarean delivery) undertaken. Because all the randomized clinical trials (RCTs) with EFM compare it with intermittent auscultation (IA), the efficacy is determined by calculating the relative risk (RR) of interventions, neonatal seizure, cerebral palsy, or death. Compared with IA, EFM is associated with a significantly increased likelihood of operative vaginal delivery, overall cesarean delivery, as well as with nonreassuring fetal heart rate tracing or fetal acidosis. Though the use of EFM and intrapartum interventions significantly decreases the rate of neonatal seizures, its use is not associated with a significantly lower rate of cerebral palsy or of neonatal death.
      American College of Obstetricians and Gynecologists
      Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles ACOG practice bulletin no. 106.
      A recent Cochrane review by Alfirevic et al
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      reported that EFM was associated with 1 additional cesarean delivery for every 58 women monitored continuously and 661 women would have to have EFM during labor to prevent 1 neonatal seizure.
      Although the efficacy of EFM is debatable, it is noteworthy that there are some concerns
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      regarding the 12 RCTs, which sampled 37,000 women. Only 2 of these trials are of high quality,
      • Renou P.
      • Chang A.
      • Anderson I.
      • Wood C.
      Controlled trial of fetal intensive care.
      • Macdonald D.
      • Grant A.
      • Sheridan-Pereira M.
      • Boylan P.
      • Chalmers I.
      The Dublin randomized controlled trial of intrapartum fetal heart rate monitoring.
      and only 3 trials reported data in low-risk women.
      • Renou P.
      • Chang A.
      • Anderson I.
      • Wood C.
      Controlled trial of fetal intensive care.
      • Macdonald D.
      • Grant A.
      • Sheridan-Pereira M.
      • Boylan P.
      • Chalmers I.
      The Dublin randomized controlled trial of intrapartum fetal heart rate monitoring.
      • Leveno K.J.
      • Cunningham F.G.
      • Nelson S.
      • et al.
      A prospective comparison of selective and universal electronic fetal monitoring in 34,995 pregnancies.
      The risk of cerebral palsy was ascertained in one trial,
      • Luthy D.A.
      • Shy K.K.
      • van Belle G.
      • et al.
      A randomized trial of electronic fetal monitoring in preterm labor.
      which randomized newborn infants at <32 weeks and risk of hypoxic ischemic encephalopathy by another.
      • Vintzileos A.M.
      • Antsaklis A.
      • Varvarigos I.
      • Papas C.
      • Sofatzis I.
      • Montgomery J.T.
      A randomized trial of intrapartum electronic fetal heart rate monitoring versus intermittent auscultation.
      The combined sample size of 12 RCTs is insufficient to determine whether EFM can significantly lower neonatal mortality. Alfirevic et al
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      noted that to test the hypothesis that continuous monitoring can prevent 1 death in 1000 births, more than 50,000 women need randomization. In addition, there are concerns that a metaanalysis that combines results of RCTs published before the introduction of the CONSORT (Consolidated Standards of Reporting Trials) guidelines
      • Begg C.
      • Cho M.
      • Eastwood S.
      • et al.
      Improving the quality of reporting of randomized controlled trials: the CONSORT statement.
      or with inadequate study sample size may not reflect the outcomes in actual practice.
      • Vintzileos A.M.
      Evidence-based compared with reality-based medicine in obstetrics.
      Thus, we sought to determine the efficacy of EFM by comparing the outcomes among women who were vs were not monitored electronically during labor.
      The primary objective of this study was to examine the association between EFM during labor and corrected neonatal and infant mortality in the United States. The secondary objectives were to assess the relative risk of operative vaginal delivery or primary cesarean delivery as well as neonatal morbidity (Apgar score <4 at 5 minutes or neonatal seizures) by EFM status.

      Materials and Methods

      We used the US 2004 birth cohort linked birth/infant death dataset assembled by the National Center for Health Statistics. Because this deidentified data are publicly available, our study was not considered as “human subjects research,” and did not require approval from the institutional review board.
      The study population consisted of singleton live births documented using the 1989 revision of the standard certificate of live birth, used by 41 states and the District of Columbia. We restricted the study to US residents, and pregnancies that ended between 24 and 44 weeks in gestation. We excluded newborn infants with congenital anomaly or implausible birthweight-gestational age combinations based on an algorithm developed by Alexander et al.
      • Alexander G.
      • Himes J.
      • Kaufman R.
      • Mor J.
      • Kogan M.
      A United States national reference for fetal growth.
      We also excluded births delivered by repeat cesarean sections. The primary outcomes included neonatal and infant mortality (death within the first year). We further categorized neonatal deaths as early neonatal (deaths within the first 6 days), late neonatal (deaths between 7-27 days), and postneonatal mortality (deaths between 28-364 days).
      In the regression analyses, the primary exposure variable was EFM status during labor (yes vs no). Covariates that were considered as potential confounders included maternal age (categorized as <20, 20-34, and ≥35 years), maternal race/ethnicity (white/non-Hispanic whites, African-American/non-Hispanic blacks, Hispanic, and other races), maternal educational attainment (categorized into less than high school, completed high school, beyond high school), marital status (currently married, not currently married), self-reported tobacco use or alcohol use during pregnancy (yes vs no), and infant's sex (male vs female). We limited our potential confounders because of concerns for overadjustment for variables in the causal pathway between the EFM and perinatal outcomes.
      • Schisterman E.F.
      • Cole S.R.
      • Platt R.W.
      Overadjustment bias and unnecessary adjustment in epidemiologic studies.
      We calculated the risk of corrected early neonatal, late neonatal, postneonatal, and infant mortality rate for EFM and non-EFM groups. Multivariable log-binomial regression models were fitted to evaluate the association between EFM and mortality with adjustments for confounders. Results are presented as adjusted risk ratio (aRR) and 95% confidence intervals. We also calculated the “number needed to treat” (NNT) to avoid 1 adverse birth outcome
      • Altman D.G.
      Confidence intervals for the number needed to treat.
      ; that is, the number of women who need to have an EFM to prevent 1 death.
      Additional secondary analyses were conducted. We compared the distribution of having operative vaginal or primary cesarean delivery based on EFM status. We estimated the relative risk of the neonatal morbidities, which include Apgar score at 5 minutes (<4 vs ≥4), neonatal seizure (yes vs no), or either 1, for all women, or those with gestational ages ≥37, <37, ≥34, <34 weeks, as well as in high- and low-risk women. Low risk was defined as all women excluding those with cardiac, acute or chronic lung disease, diabetes, hydramnios or oligohydramnios, hemoglobinopathy, chronic hypertension, pregnancy-induced hypertension, eclampsia, renal disease, Rh sensitization, uterine bleeding, and preterm delivery (gestational age <37 weeks). High risk was defined as gestational age <37 weeks or presence of any of the above high-risk factors.
      The proportion of data with missing values for each covariate was <2%. All analyses were performed using SAS 9.2 (SAS Institute, Inc, Cary, NC.)

      Results

      In 2004, there were 4,118,956 live births in the United States. We excluded 6903 births to foreign resident mothers, 139,494 births with multiple gestation, 80,374 newborn infants delivered before 24 weeks or after 44 weeks, 13,847 infants with implausible birthweights, 422,396 infants delivered by repeat cesarean sections, 38,013 anomalous neonates, 793,571 births using the 2003 revision of the standard certificate, 888,774 infants from areas where variables used in the analyses were not reported, and 3373 infants with unknown use of EFM. After these exclusions, there were 1,732,211 singleton live births (42% of all live births) that comprised our study population, of whom 89% used EFM during labor. Table 1 presents the sample characteristics.
      TABLE 1Sample characteristics
      Mortality
      CharacteristicsTotal live births (n = 1,732,211)Early neonatal (n = 1568)Late neonatal (n = 919)Post-neonatal (n = 2927)Infant (n = 5414)
      Mother's age, y
       <2011% (196,225)17% (266)20% (186)21% (624)20% (1076)
       20–3476% (1,322,142)71% (1120)70% (644)72% (2097)71% (3861)
       ≥3512% (213,844)12% (182)10% (89)7% (206)9% (477)
      Mother's race/ethnicity
       White/non-Hispanic63% (1,090,445)49% (755)50% (457)53% (1551)51% (2763)
       Black/non-Hispanic16% (281,740)34% (523)33% (303)31% (915)32% (1741)
       Hispanic14% (247,710)13% (195)13% (121)10% (298)11% (614)
       Other/non-Hispanic6% (99,235)5% (80)4% (33)5% (146)5% (259)
      Mother's marital status
       Nonmarried37% (635,672)53% (836)58% (532)63% (1832)59% (3200)
       Married63% (1,096,539)47% (732)42% (387)37% (1095)41% (2214)
      Mother's education
       Less than high school19% (332,758)26% (392)29% (255)35% (1022)32% (1669)
       High school completed30% (515,557)36% (545)37% (326)36% (1051)36% (1922)
       Above high school50% (863,027)37% (561)35% (309)28% (821)32% (1691)
      Use of tobacco
       No89% (1,528,545)85% (1313)76% (696)72% (2089)77% (4098)
       Yes11% (194,339)15% (233)24% (218)28% (806)23% (1257)
      Use of alcohol
       No99% (1,710,120)98% (1519)98% (897)98% (2855)98% (5721)
       Yes1% (12,457)2% (25)2% (18)2% (46)2% (89)
      Infant sex
       Female49% (847,007)41% (636)40% (371)41% (1188)41% (2195)
       Male51% (885,204)59% (932)60% (548)59% (1739)59% (3219)
      Electronic fetal monitoring
       No11% (195,940)21% (324)12% (112)12% (349)14% (785)
       Yes89% (1,536,271)79% (1244)88% (807)88% (2578)86% (4629)
      Data presented as % (n).
      Chen. Electronic fetal monitoring and mortality. Am J Obstet Gynecol 2011.
      The corrected early neonatal, late neonatal, postneonatal, and infant mortality rates for all subjects were 0.9, 0.5, 1.7, and 3.1 per 1000 births, respectively. Figure 1 presents the mortality rate by EFM groups. The risk of corrected mortality rate was different between those with vs without EFM during the early neonatal period (0.8 vs 1.7 per 1000 births, respectively; P < .001), but not in late (0.5 vs 0.6; P = .402) or postneonatal periods (1.7 vs 1.8; P = .296). The corrected infant mortality rate was 3.0 per 1000 births for those with EFM and was significantly lower than 4.0 per 1000 births for those without EFM (P < .001).
      Figure thumbnail gr1
      FIGURE 1Risk of mortality rate among women with or without EFM during labor
      Early neonatal and infant mortality rates were significantly different (P < .001 for each comparison), but late neonatal (P = .402) and postneonatal (P = .296) mortality were similar. Mortality rates are shown on a logarithmic scale.
      EFM, electronic fetal monitoring.
      Chen. Electronic fetal monitoring and mortality. Am J Obstet Gynecol 2011.
      Gestational age-specific early neonatal mortality differed significantly among those with vs without EFM (Figure 2). Table 2 presents the adjusted RR of mortality and neonatal morbidity, according to gestational age at birth and EFM use. Having EFM during labor was associated with a lower risk of early neonatal deaths (RR, 0.50) and a reduced risk of having Apgar score <4, regardless of gestational age. EFM was also significantly associated with a lower risk of infant mortality (RR, 0.75), particularly for births within 24-27, 28-31, 32-33, and ≥37 gestational weeks.
      Figure thumbnail gr2
      FIGURE 2Gestational age-specific early neonatal mortality rate among women with or without EFM
      Gestational age-specific early neonatal mortality rate among women with or without EFM (P < .001 for all comparisons, except for 32-33 weeks, for which P = .001). Mortality rates are shown on a logarithmic scale.
      EFM, electronic fetal monitoring.
      Chen. Electronic fetal monitoring and mortality. Am J Obstet Gynecol 2011.
      TABLE 2Mortality and neonatal morbidity by gestational ages for pregnancies with EFM compared to those without EFM
      Gestational ages, wkMortalityMorbidity
      Early neonatalLate neonatalPostneonatalInfantApgar score <4Neonatal seizuresApgar score <4 or neonatal seizures
      (0-6 d)(7-27 d)(28-364 d)(0-364 d)
      All0.50 (0.44–0.57)
      95% confidence intervals do not cross 1.
      0.91 (0.74–1.12)0.91 (0.81–1.02)0.75 (0.69–0.81)
      95% confidence intervals do not cross 1.
      0.54 (0.49–0.59)
      95% confidence intervals do not cross 1.
      0.85 (0.70–1.03)0.60 (0.55–0.65)
      95% confidence intervals do not cross 1.
      24-270.63 (0.54–0.72)
      95% confidence intervals do not cross 1.
      0.97 (0.72–1.31)1.06 (0.77–1.45)0.78 (0.70–0.87)
      95% confidence intervals do not cross 1.
      0.58 (0.50–0.67)
      95% confidence intervals do not cross 1.
      IC
      Incalculable because there were 10 or less neonatal seizures;
      0.61 (0.53–0.72)
      95% confidence intervals do not cross 1.
      28-310.51 (0.37–0.70)
      95% confidence intervals do not cross 1.
      1.25 (0.67–2.33)0.98 (0.65–1.49)0.75 (0.60–0.95)
      95% confidence intervals do not cross 1.
      0.55 (0.41–0.74)
      95% confidence intervals do not cross 1.
      0.49 (0.16–1.49)0.57 (0.43–0.76)
      95% confidence intervals do not cross 1.
      32-330.39 (0.21–0.75)
      95% confidence intervals do not cross 1.
      0.88 (0.31–2.52)0.83 (0.47–1.49)0.66 (0.44–0.98)
      95% confidence intervals do not cross 1.
      0.49 (0.31–0.78)
      95% confidence intervals do not cross 1.
      IC
      Incalculable because there were 10 or less neonatal seizures;
      0.55 (0.34–0.86)
      95% confidence intervals do not cross 1.
      34-360.41 (0.24–0.71)
      95% confidence intervals do not cross 1.
      1.08 (0.54–2.15)1.03 (0.73–1.44)0.87 (0.67–1.13)0.48 (0.36–0.64)
      95% confidence intervals do not cross 1.
      0.80 (0.45–1.43)0.54 (0.42–0.70)
      95% confidence intervals do not cross 1.
      >370.65 (0.47–0.90)
      95% confidence intervals do not cross 1.
      0.90 (0.63–1.27)0.89 (0.78–1.03)0.86 (0.76–0.97)
      95% confidence intervals do not cross 1.
      0.62 (0.54–0.71)
      95% confidence intervals do not cross 1.
      0.86 (0.70–1.07)0.68 (0.61–0.77)
      95% confidence intervals do not cross 1.
      Data presented as adjusted relative risk (95% confidence intervals). Analyses adjusted for maternal age, maternal race/ethnicity, marital status, education, tobacco use, alcohol use, and newborn infant's sex.
      EFM, electronic fetal monitoring; IC, incalculable.
      Chen. Electronic fetal monitoring and mortality. Am J Obstet Gynecol 2011.
      a Incalculable because there were 10 or less neonatal seizures;
      b 95% confidence intervals do not cross 1.
      Table 3 presents the number needed to treat (NNT) (the number of EFMs that need to be performed) to prevent 1 death. There is a positive correlation between gestational age and NNT to prevent early neonatal and infant death. For infant mortality, the NNT ranged from as low as 1:15 for gestations 24-27 weeks to as high as 1:4078 for term gestations.
      TABLE 3Number of pregnancies needed in the EFM (NNT) to prevent 1 neonatal or infant death
      Analyses adjusted for maternal age, maternal race/ethnicity, marital status, education, tobacco use, alcohol use, and newborn infant's sex.
      Gestational ages, wkEarly neonatal mortalityInfant mortality
      NNT95% CINNT95% CI
      All12661073–15421012798–1352
      24-27129–171510–28
      28-317148–1318246–424
      32-33291174–887217112–3472
      34-361449912–35291753NNTB 611–infine–NNTH 2016
      ≥3710,9496275–42,92140782232–23,646
      CI, confidence interval; EFM, electronic fetal monitoring; NNT, number needed to treat (number of women who need to have electronic monitoring to prevent one death); NNTB, NNT (benefit); NNTH, NNT (harm).
      Chen. Electronic fetal monitoring and mortality. Am J Obstet Gynecol 2011.
      a Analyses adjusted for maternal age, maternal race/ethnicity, marital status, education, tobacco use, alcohol use, and newborn infant's sex.
      The likelihood of having an operative vaginal delivery or primary cesarean delivery based on EFM status is shown in Table 4. The risk of having an operative delivery was higher in the EFM group than in the no EFM group (RR, 1.39), especially when it was related to fetal distress (RR, 1.82). There was also a higher risk of having a primary cesarean delivery related to fetal distress in the EFM group than in the no EFM group (RR, 1.81).
      TABLE 4Operative delivery or primary cesarean delivery based on electronic fetal monitoring status
      VariableEFM, % (n = 1,526,758)
      There were 0.6% (EFM) and 0.7% (No EFM) missing data of delivery method;
      No EFM, % (n = 194,527)
      There were 0.6% (EFM) and 0.7% (No EFM) missing data of delivery method;
      RR (95% CI)
      Operative vaginal delivery
      Forceps or vacuum;
      6.24.51.39 (1.34–1.42)
      95% CIs do not cross 1.
      Operative vaginal delivery for fetal distress
      Fetal intolerance of labor such that 1 or more of the following actions was taken: in utero resuscitation measures, further fetal assessment, or operative delivery;
      0.60.31.82 (1.67–1.97)
      95% CIs do not cross 1.
      Primary cesarean delivery17.717.80.99 (0.98–1.00)
      Primary cesarean delivery for fetal distress
      Fetal intolerance of labor such that 1 or more of the following actions was taken: in utero resuscitation measures, further fetal assessment, or operative delivery;
      2.81.51.81 (1.74–1.88)
      95% CIs do not cross 1.
      CI, confidence interval; EFM, electronic fetal monitoring; RR, relative risk.
      Chen. Electronic fetal monitoring and mortality. Am J Obstet Gynecol 2011.
      a There were 0.6% (EFM) and 0.7% (No EFM) missing data of delivery method;
      b Forceps or vacuum;
      c Fetal intolerance of labor such that 1 or more of the following actions was taken: in utero resuscitation measures, further fetal assessment, or operative delivery;
      d 95% CIs do not cross 1.
      Table 5 presents the RR of neonatal morbidity for all women, those with gestational age ≥37, <37, ≥34, <34 weeks, as well for high- and low-risk women. There was a significantly lower risk of having an Apgar score <4 at 5 minutes in the EFM group than in the no EFM group, in all groups analyzed. In addition, EFM was associated with decreased risk for neonatal seizures in high-risk pregnancies (adjusted RR, 0.65; 95% confidence interval, 0.46–0.94).
      TABLE 5Relative risk of neonatal morbidity based upon EFM status (EFM vs no EFM)
      VariableEFMNo EFMRR (95% CI)
      All gestational ages(n = 1,536,271)(n = 195,940)
       Apgar score <4 at 5 min1.62.90.54 (0.49–0.51)
      95% CIs do not cross 1.
       Neonatal seizures0.50.60.84 (0.70–1.02)
       Apgar score <4 at 5 min or neonatal seizures2.13.50.60 (0.55–0.65)
      95% CIs do not cross 1.
      Gestational age ≥37 wk(n = 1,380,348)(n = 175,904)
       Apgar score <4 at 5 min0.91.40.62 (0.54–0.71)
      95% CIs do not cross 1.
       Neonatal seizures0.50.60.86 (0.70–1.05)
       Apgar score <4 at 5 min or neonatal seizures1.42.00.69 (0.62–0.77)
      95% CIs do not cross 1.
      Gestational age <37 wk(n = 155,923)(n = 20,036)
       Apgar score <4 at 5 min8.016.80.48 (0.42–0.54)
      95% CIs do not cross 1.
       Neonatal seizures0.71.00.78 (0.48–1.27)
       Apgar score <4 at 5 min or neonatal seizures8.617.10.50 (0.45–0.57)
      95% CIs do not cross 1.
      Gestational age ≥34 wk(n = 1,500,402)(n = 191,028)
       Apgar score <4 at 5 min1.01.60.59 (0.52–0.60)
      95% CIs do not cross 1.
       Neonatal seizures0.50.60.85 (0.70–1.03)
       Apgar score <4 at 5 min or neonatal seizures1.52.20.66 (0.59–0.73)
      95% CIs do not cross 1.
      Gestational age <34 wk(n = 35,869)(n = 4912)
       Apgar score <4 at 5 min28.255.70.51 (0.55–0.73)
      95% CIs do not cross 1.
       Neonatal seizures0.81.00.80 (0.31–2.05)
       Apgar score <4 at 5 min or neonatal seizures28.754.00.53 (0.47–0.61)
      95% CIs do not cross 1.
      Low risk
      Low risk excludes women with cardiac, acute or chronic lung disease, diabetes, hydramnios/oligohydramnios, hemoglobinopathy, chronic hypertension, pregnancy associated hypertension, eclampsia, renal disease, Rh sensitization, uterine bleeding, and preterm (gestational age <37 wk);
      (n = 1,228,360)(n = 162,804)
       Apgar score <4 at 5 min0.81.30.62 (0.53–0.72)
      95% CIs do not cross 1.
       Neonatal seizures0.50.50.91 (0.72–1.13)
       Apgar score <4 at 5 min or neonatal seizures1.31.80.70 (0.62–0.79)
      95% CIs do not cross 1.
      High-risk
      High risk: women with gestational age <37 wk or with cardiac, acute or chronic lung disease, diabetes, hydramnios/oligohydramnios, hemoglobinopathy, chronic hypertension, pregnancy associated hypertension, eclampsia, renal disease, Rh sensitization, and uterine bleeding;
      (n = 307,911)(n = 33,136)
       Apgar score <4 at 5 min4.711.00.43 (0.38–0.48)
      95% CIs do not cross 1.
       Neonatal seizures0.71.10.65 (0.46–0.94)
      95% CIs do not cross 1.
       Apgar score <4 at 5 min or neonatal seizures5.311.70.45 (0.40–0.50)
      95% CIs do not cross 1.
      Data presented as rate per 1000 births.
      CI, confidence interval; EFM, electronic fetal monitoring; RR, relative risk.
      Chen. Electronic fetal monitoring and mortality. Am J Obstet Gynecol 2011.
      a Low risk excludes women with cardiac, acute or chronic lung disease, diabetes, hydramnios/oligohydramnios, hemoglobinopathy, chronic hypertension, pregnancy associated hypertension, eclampsia, renal disease, Rh sensitization, uterine bleeding, and preterm (gestational age <37 wk);
      b High risk: women with gestational age <37 wk or with cardiac, acute or chronic lung disease, diabetes, hydramnios/oligohydramnios, hemoglobinopathy, chronic hypertension, pregnancy associated hypertension, eclampsia, renal disease, Rh sensitization, and uterine bleeding;
      c 95% CIs do not cross 1.

      Comment

      Intrapartum assessment of the fetus is imperative. Despite EFM being the most common modality during labor to assess fetal well-being, it is not used universally. In the United States, between 1997 and 2003, EFM was not used with 15-17% of deliveries.
      • Ventura S.J.
      • Martin J.A.
      • Curtin S.C.
      • Mathews T.J.
      Births: final data for 1997.
      • Ventura S.J.
      • Martin J.A.
      • Curtin S.C.
      • Mathews T.J.
      • Park M.M.
      Births: final data for 1998.
      • Ventura S.J.
      • Martin J.A.
      • Curtin S.C.
      • Menacker F.
      • Hamilton B.E.
      Births: final data for 1999.
      • Martin J.A.
      • Hamilton B.E.
      • Ventura S.J.
      • Menacker F.
      • Park M.M.
      Births: final data for 2000.
      • Martin J.A.
      • Hamilton B.E.
      • Ventura S.J.
      • Menacker F.
      • Park M.M.
      • Sutton P.D.
      Births: final data for 2001.
      • Martin J.A.
      • Hamilton B.E.
      • Sutton P.D.
      • Ventura S.J.
      • Menacker F.
      • Munson M.L.
      Births: final data for 2002.
      • Martin J.A.
      • Hamilton B.E.
      • Sutton P.D.
      • et al.
      Births: final data for 2003.
      The possible explanations for not using EFM include women undergoing repeat cesarean delivery, clinician's preference for IA,
      • Sandmire H.F.
      • DeMott R.K.
      Intrapartum fetal heart rate assessment: which method is superior.
      American College of Nurse-Midwives
      Intermittent auscultation for intrapartum fetal heart rate surveillance (replaces ACNM Clinical Bulletin 9, March 2007).
      planned home births,
      • Wax J.R.
      • Lucas F.L.
      • Lamont M.
      • Pinette M.G.
      • Cartin A.
      • Blackstone J.
      Maternal and newborn outcomes in planned home birth vs. planned hospital births: a meta analysis.
      precipitous delivery,
      • Robinson L.
      Preparing for precipitous vaginal deliveries in the emergency department.
      • Lewis D.F.
      • Robichaux A.G.
      • Jaekle R.K.
      • et al.
      Expectant management of preterm premature rupture of membranes and nonvertex presentation: what are the risks?.
      nonavailability of EFM during busy hours, and not using EFM at the limit of viability.
      • Morgan M.A.
      • Goldenberg R.L.
      • Schulkin J.
      Obstetrician-gynecologists' practices regarding preterm birth at the limit of viability.
      Regardless of the reasons why EFM was not used and whether repeat cesarean deliveries are excluded, a comparison of peripartum outcomes of women who had vs those who did not have EFM suggests a potential benefit of monitoring.

      Principal findings

      The primary finding of this study is that EFM use during labor was associated with a significantly lower early neonatal and infant mortality. In fact, NNT calculations suggest that as gestational age decreases, the NNT to monitor and prevent 1 early neonatal death drops drastically. At gestational age of 24-27 weeks, the NNT was 12, but at ≥37 weeks, it was 10,949. Potential reasons for why EFM is more likely to avert early neonatal deaths among preterm than term births are that preterm deliveries are associated with medical or obstetric complications; preterm fetuses are more prone to hypoxia and acidosis often because of underlying placental disease,
      • Altman D.G.
      Confidence intervals for the number needed to treat.
      have higher rate of perinatal mortality,
      • Ananth C.V.
      • Vintzileos A.M.
      Maternal-fetal conditions necessitating a medical intervention resulting in preterm birth.
      are more likely to have precipitous delivery,
      • Ananth C.V.
      • Joseph K.S.
      • Demissie K.
      • Vintzileos A.M.
      Trends in preterm birth and perinatal mortality among singletons: United States, 1989 through 2000.
      and continuous monitoring is used infrequently, especially at the limits of viability. There is biologic plausibility for why EFM is associated with decreased mortality: certain fetal heart patterns (eg, recurrent late, absence of variability, and prolonged bradycardia) precede fetal hypoxia, acidemia, and death. A reasonable speculation is that the better neonatal outcomes associated with the use of EFM may be due to appropriate timing of obstetric interventions and delivery because of more accurate and earlier detection of fetal acidemia by EFM.
      • Vintzileos A.M.
      • Nochimson D.J.
      • Antsaklis A.
      • Varvarigos I.
      • Guzman E.R.
      • Knuppel R.A.
      Comparison of intrapartum electronic fetal heart rate monitoring versus intermittent auscultation in detecting fetal acidemia at birth.
      • Hadar A.
      • Sheiner E.
      • Hallak M.
      • Katz M.
      • Mazor M.
      • Shoham-Vardi I.
      Abnormal fetal heart rate tracing patterns during the first stage of labor: effect on perinatal outcome.
      • Low J.A.
      • Killen H.
      • Derrick E.J.
      The prediction and prevention of intrapartum fetal asphyxia in preterm pregnancies.
      • Norén H.
      • Amer-Wåhlin I.
      • Hagberg H.
      • et al.
      Fetal electrocardiography in labor and neonatal outcome: data from the Swedish randomized controlled trial on intrapartum fetal monitoring.
      • Williams K.P.
      • Galerneau F.
      Intrapartum fetal heart rate patterns in the prediction of neonatal acidemia.
      • Sameshima H.
      • Ikenoue T.
      • Ikeda T.
      • Kamitomo M.
      • Ibara S.
      Unselected low-risk pregnancies and the effect of continuous intrapartum fetal heart rate monitoring on umbilical blood gases and cerebral palsy.
      • Larma J.D.
      • Silva A.M.
      • Holcroft C.J.
      • Thompson R.E.
      • Donohue P.K.
      • Graham E.M.
      Intrapartum electronic fetal heart rate monitoring and the identification of metabolic acidosis and hypoxic-ischemic encephalopathy.
      • Xu H.
      • Mas-Calvet M.
      • Wei S.Q.
      • Luo Z.C.
      • Fraser W.D.
      Abnormal fetal heart rate tracing patterns in patients with thick meconium staining of the amniotic fluid: association with perinatal outcomes.
      Our secondary analyses are informative. Use of EFM was associated with an increased likelihood of operative vaginal delivery for all indications, as well as for fetal distress. In addition, use of continuous monitoring was associated with an increased risk of primary cesarean delivery for fetal distress, though not for all indications. Admittedly, the definition of fetal distress in daily clinical practice
      • Chauhan S.P.
      • Roach H.
      • Naef R.W.
      • Magann E.F.
      • Morrison J.C.
      • Martin Jr, J.N.
      Cesarean section for suspected fetal distress: does the decision-incision time make a difference?.
      may differ from the one documented on birth certificates, which do not provide detailed information on the nature of distress. However, it is noteworthy that Alfirevic et al
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      also noted that compared with IA, EFM is linked with an increased rate of operative vaginal deliveries and cesarean deliveries.
      Additional analysis also indicates that regardless of gestational age, and type of pregnancy (high- or low-risk), use of EFM was associated with a lower likelihood of 5-minute Apgar score <4. Casey et al
      • Casey B.M.
      • McIntire D.D.
      • Leveno K.J.
      The continuing value of the Apgar score for the assessment of newborn infants.
      reported that newborn infants with 5-minute Apgar score <4 had significantly lower rate of neonatal survival, whether they were preterm (26-36 weeks) or term (≥37 weeks). Among preterm births, for example, the neonatal mortality rate was 315 per 1000 births when the Apgar score was <4 and 5 per 1000 when the score was ≥7. The corresponding numbers for term newborn infants were 244 vs 0.2 per 1000, respectively. These investigators
      • Casey B.M.
      • McIntire D.D.
      • Leveno K.J.
      The continuing value of the Apgar score for the assessment of newborn infants.
      also noted that low Apgar score was associated with early neonatal death “at no more than 1 day of age,” for preterm and term infants. Thus, a plausible pathway for EFM to decrease early neonatal mortality is through lowering the likelihood of 5-minute Apgar score <4.
      The secondary analysis also indicates that the rate of neonatal seizure was significantly lower only among high-risk women who had EFM. Both the Cochrane review
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      and a metaanalysis
      • Graham E.M.
      • Petersen S.M.
      • Christo D.K.
      • Fox H.E.
      Intrapartum electronic fetal heart rate monitoring and the prevention of perinatal brain injury.
      have confirmed that compared with IA, EFM use is associated with a lower rate of seizure in newborn infants. Our study extends their finding and specifies the population that EFM is most likely to influence the rate of seizure. Our finding also supports the ACOG recommendation
      American College of Obstetricians and Gynecologists
      Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles ACOG practice bulletin no. 106.
      that high-risk women should be monitored via EFM rather than IA. Althaus et al
      • Althaus J.E.
      • Petersen S.M.
      • Fox H.E.
      • Holcroft C.J.
      • Graham E.M.
      Can electronic fetal monitoring identify preterm neonates with cerebral white matter injury?.
      reported that fetal heart monitoring during labor did not identify preterm newborn infants with white matter injury. This may be a possible explanation of why our analysis noted that seizure activity was similar between the 2 groups.

      Clinical and research implications

      According to the Cochrane review
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      and the most recent ACOG recommendation,
      American College of Obstetricians and Gynecologists
      Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles ACOG practice bulletin no. 106.
      the use of fetal heart rate monitoring increases operative delivery rate without a concomitant decrease in long-term neonatal outcomes. Thus, understandably there has been continued angst about using fetal heart rate monitoring during labor.
      • Sandmire H.F.
      Whither electronic fetal monitoring?.
      • Rosen M.G.
      • Dickinson J.C.
      The paradox of electronic fetal monitoring: more data may not enable us to predict or prevent infant neurologic morbidity.
      • Parer J.T.
      • King T.
      Fetal heart rate monitoring: is it salvageable?.
      • Clark S.L.
      • Hankins G.D.
      Temporal and demographic trends in cerebral palsy—fact and fiction.
      • Low J.A.
      The current crisis in obstetrics.
      • Grimes D.A.
      Epidemiologic research using administrative databases: garbage in, garbage out.
      The main implication of our study is that now there is reassuring evidence for the use of EFM; its use is linked with long-term improvements: a significant decrease in early neonatal and infant mortality, of lowering the likelihood of 5-minute Apgar < 4, and reduced risk of neonatal seizures. Thus, although studies on the performance of other diagnostic modalities, like ST segment analysis (STAN) as an adjunct to EFM
      • Belfort M.A.
      • Saade G.R.
      ST Segment Analysis (STAN) as an adjunct to electronic fetal monitoring, part II: clinical studies and future directions.
      are underway, fetal heart rate monitoring can be used in daily practice with some assurance.
      A conclusion of the study is the large sample size necessary to demonstrate improvement in neonatal outcomes. One reason the metaanalysis
      • Graham E.M.
      • Petersen S.M.
      • Christo D.K.
      • Fox H.E.
      Intrapartum electronic fetal heart rate monitoring and the prevention of perinatal brain injury.
      and Cochrane review
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      did not demonstrate benefit of EFM is small sample size of published reports. Alfirevic et al
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      acknowledged that over 50,000 women need to be randomized to demonstrate improvement in mortality. The issue of sufficient sample size to demonstrate that EFM, or any other modality, can reduce neonatal encephalopathy attributable to intrapartum event remains unachievable in modern day obstetrics. It is estimated that only 1.6 newborn infants per 10,000 births will have neonatal encephalopathy in the absence of preconceptual or antenatal events.
      American College of ObstetriciansGynecologists' Task Force on National EncephalopathyCerebral PalsyAmerican College of ObstetriciansGynecologistsAmerican Academy of Pediatrics
      Neonatal encephalopathy and cerebral palsy: defining the pathogenesis and pathophysiology.
      Thus, to determine whether EFM can reduce neonatal encephalopathy secondary to an intrapartum event by 30%, over 38 million women need to be randomized to each arm of the RCT (assuming a type I error probability of 0.05 and a type II error probability of 0.2). Thus, when the outcomes are uncommon and randomized trials are not plausible, we should consider evidence from “reality-based medicine,”
      • Vintzileos A.M.
      Evidence-based compared with reality-based medicine in obstetrics.
      for it, along with this study, demonstrates improvement in mortality with EFM.
      • Fretts R.C.
      • Schmittdiel J.
      • McLean F.H.
      • Usher R.H.
      • Goldman M.B.
      Increased maternal age and the risk of fetal death.
      • Fretts R.C.
      • Boyd M.E.
      • Usher R.H.
      • Usher H.A.
      The changing pattern of fetal death, 1961-1988.
      Our analysis of NNT to prevent one neonatal or infant death has important clinical implications. Preterm fetuses are inherently at increased risk of mortality and they should be monitored carefully during labor. Admittedly, it is more difficult to monitor these fetuses, and what is reassuring fetal heart rate tracing may be different for those at least vs greater than 32 weeks' gestation.
      American College of Obstetricians and Gynecologists
      Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles ACOG practice bulletin no. 106.
      However, there is evidence that the fetal heart rate pattern among preterm newborn infants is linked to postnatal morbidities and mortality.
      • Holmes P.
      • Oppenheimer L.W.
      • Gravelle A.
      • Walker M.
      • Blayney M.
      The effect of variable heart rate decelerations on intraventricular hemorrhage and other perinatal outcomes in preterm infants.
      • Ayoubi J.M.
      • Audibert F.
      • Boithias C.
      • et al.
      Perinatal factors affecting survival and survival without disability of extreme premature infants at two years of age.
      • Ayoubi J.M.
      • Audibert F.
      • Vial M.
      • Pons J.C.
      • Taylor S.
      • Frydman R.
      Fetal heart rate and survival of the very premature newborn.
      The finding of significantly increased operative vaginal and primary cesarean deliveries with EFM also has implications. When emergency cesarean delivery is done for nonreassuring fetal heart rate tracing, the umbilical arterial pH is less than 7.0 in 4 to 10% of the cases.
      • Chauhan S.P.
      • Magann E.F.
      • Scott J.R.
      • Scardo J.A.
      • Hendrix N.W.
      • Martin Jr, J.N.
      Emergency cesarean delivery for nonreassuring fetal heart rate tracings: compliance with ACOG guidelines.
      • Nasrallah F.K.
      • Harirah H.M.
      • Vadhera R.
      • Jain V.
      • Franklin L.T.
      • Hankins G.D.
      The 30-minute decision-to-incision interval for emergency cesarean delivery: fact or fiction?.
      • Bloom S.L.
      • Leveno K.J.
      • Spong C.Y.
      • et al.
      National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network Decision-to-incision times and maternal and infant outcomes.
      A possible reason for the lack of objective evidence of fetal compromise at birth with operative interventions may be the fact that the operative interventions are early enough to prevent adverse outcome. Indeed, it has been argued by Freeman and Nageotte
      • Freeman R.K.
      • Nageotte M.P.
      Comments on American College of Obstetricians and Gynecologists practice bulletin no. 106.
      that the “high-false positive” rate of EFM results could be the results of timely interventions, which prevent perinatal mortality.
      Another issue to consider is that clinicians do not usually undertake intrauterine resuscitative measures before proceeding with emergency cesarean. In a majority of the cases, clinicians do not use scalp or fetal acoustic stimulation to elicit acceleration, attempt amnioinfusion for variable decelerations, or administer tocolytics to resolve the fetal heart abnormalities.
      • Chauhan S.P.
      • Magann E.F.
      • Scott J.R.
      • Scardo J.A.
      • Hendrix N.W.
      • Martin Jr, J.N.
      Emergency cesarean delivery for nonreassuring fetal heart rate tracings: compliance with ACOG guidelines.
      • Hendrix N.W.
      • Chauhan S.P.
      • Scardo J.A.
      • Ellings J.M.
      • Devoe L.D.
      Managing nonreassuring fetal heart rate patterns before cesarean delivery: compliance with ACOG recommendations.
      It is our belief that clinicians should improve compliance with intrauterine resuscitation, although additional research is being done to decrease operative rate, without increasing neonatal morbidity and mortality.

      Strengths and weaknesses

      The major strength of the study is the large sample size, sufficient to demonstrate a substantial beneficial effect of EFM in reducing mortality rates for newborn infants. Considering the deliveries that occurred across the United States in contemporary practice, these finding are generalizable. We excluded women with prior cesarean deliveries, multiple gestation, documented anomalies, and implausible birthweight, which allowed us to compare our findings with previously published reports on the topic. Our notable strength also includes consistency with prior publications, including metaanalyses. Vintzileos et al
      • Vintzileos A.M.
      • Nochimson D.J.
      • Guzman E.R.
      • Knuppel R.A.
      • Lake M.
      • Schifrin B.S.
      Intrapartum electronic fetal heart rate monitoring versus intermittent auscultation: a meta-analysis.
      noted that 1 fetal death is averted for every 1000 women monitored electronically; we noted that NNT to prevent 1 early neonatal death is 1266. Alfirevic et al
      • Alfirevic Z.
      • Devane D.
      • Gyte G.M.
      Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.
      reported that use of continuous cardiotocogram is associated with increase in operative rate for fetal distress with concomitant decrease in neonatal seizures. Similarly, our analysis noted increased rate of primary cesarean delivery rate and of operative vaginal births, with concurrent decrease in neonatal seizures in high-risk pregnancies. The strength of our analysis also includes biologic plausibility: EFM decreases the likelihood of low 5-minute Apgar score, which is linked with early neonatal death.
      • Casey B.M.
      • McIntire D.D.
      • Leveno K.J.
      The continuing value of the Apgar score for the assessment of newborn infants.
      The weakness of the study should be acknowledged. Studies based on birth certificates have been criticized because of the quality of the data.
      • Grimes D.A.
      Epidemiologic research using administrative databases: garbage in, garbage out.
      However, information on the route of delivery and Apgar scores, the main variables used in the secondary analysis, are considered reliable.
      • Northam S.
      • Knapp T.R.
      The reliability and validity of birth certificates.
      Our study excluded 58% of the women who delivered in 2004 and therefore there is a potential for bias. We minimized the potential bias by selecting the exclusion criteria based on clinical necessity a priori to the analysis. Moreover, the 2 leading exclusions were infants from areas where variables used in the analyses were not reported (n = 888,774) and births documented using the 2003 revision of the standard certificate (n = 793,571). Among these 2 groups of women excluded, the results of the mortality rates were consistent with those of the women included in detailed analysis. Specifically, the early neonatal mortality with EFM was 0.7 vs 1.0 for without monitoring (P < .001) and infant mortality of 2.4 vs 2.8, respectively, (P = .006); the rate of late (0.4 vs 0.4; P = .951) and postneonatal mortality (1.3 vs 1.4; P = .630) were similar. Thus, we did minimize the potential bias.
      Additional weakness of the study involves excluded stillbirths because from birth certificates, it is difficult to be certain if the death occurred during antepartum vs intrapartum period. In addition, we limited our analysis to nonanomalous singletons and those without prior cesarean delivery. Thus, it is not feasible to extrapolate our findings to multiple gestation, or women attempting trial of labor after previous cesarean delivery.
      American College of ObstetriciansGynecologists
      Vaginal birth after previous cesarean delivery ACOG practice bulletin no. 115.
      ACOG has recently published a 3-tiered classification of fetal heart rate tracings and how to manage them.
      American College of Obstetricians and Gynecologists
      Management of intrapartum fetal heart rate tracings ACOG practice bulletin no. 116.
      In addition, there is a 5-tier color coded classification of EFM, which has been linked to neonatal metabolic acidosis and neurologic injury.
      • Parer J.T.
      • Hamilton E.F.
      Comparison of 5 experts and computer analysis in rule-based fetal heart rate interpretation.
      • Elliott C.
      • Warrick P.A.
      • Graham E.
      • Hamilton E.F.
      Graded classification of fetal heart rate tracings: association with neonatal metabolic acidosis and neurologic morbidity.
      Though it can be argued that with adoption of uniform interpretation and management of EFM of either classification system, our finding may not be applicable in the future, we think otherwise. If anything, categorization into 3 or 5 groups with consistent management may decrease the unnecessary operative deliveries while continuing to improve the outcome. Ideally, there should be CONSORT compliant RCTs
      • Begg C.
      • Cho M.
      • Eastwood S.
      • et al.
      Improving the quality of reporting of randomized controlled trials: the CONSORT statement.
      with long-term follow-up of the newborn infants to determine the benefits of EFM. However, such a large trial is infeasible.
      Randomized trials combining EFM with other diagnostic modalities, like STAN, to decrease neonatal morbidity and mortality are alluring options worth undertaking.
      • Belfort M.A.
      • Saade G.R.
      ST Segment Analysis (STAN) as an adjunct to electronic fetal monitoring, part II: clinical studies and future directions.
      • Vayssière C.
      • David E.
      • Meyer N.
      • et al.
      A French randomized controlled trial of ST-segment analysis in a population with abnormal cardiotocograms during labor.
      • Westerhuis M.E.
      • Moons K.G.
      • van Beek E.
      • et al.
      A randomised clinical trial on cardiotocography plus fetal blood sampling versus cardiotocography plus ST-analysis of the fetal electrocardiogram (STAN) for intrapartum monitoring.
      The optimism for these RCTs, however, should be tempered as evidenced by experience with fetal pulse oximetry. Initial randomized trials were positive,
      • Garite T.J.
      • Dildy G.A.
      • McNamara H.
      • et al.
      A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of nonreassuring fetal heart rate patterns.
      • Kühnert M.
      • Schmidt S.
      Intrapartum management of nonreassuring fetal heart rate patterns: a randomized controlled trial of fetal pulse oximetry.
      • Klauser C.K.
      • Christensen E.E.
      • Chauhan S.P.
      • et al.
      Use of fetal pulse oximetry among high-risk women in labor: a randomized clinical trial.
      • East C.E.
      • Brennecke S.P.
      • King J.F.
      • Chan F.Y.
      • Colditz P.B.
      FOREMOST Study Group
      The effect of intrapartum fetal pulse oximetry, in the presence of a nonreassuring fetal heart rate pattern, on operative delivery rates: a multicenter, randomized, controlled trial (the FOREMOST trial).
      until the open vs masked trial reported no improvement with neonatal outcomes.
      • Bloom S.L.
      • Spong C.Y.
      • Thom E.
      • et al.
      National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network Fetal pulse oximetry and cesarean delivery.
      Even if an RCT with EFM and/or STAN reduces composite neonatal morbidity, it may be criticized for lacking external validity or having primary outcomes, which combined events of different severity,
      • Rothwell P.M.
      External validity of randomised controlled trials: ”to whom do the results of this trial apply?”.
      may or not be adopted in daily practice.
      • Parer J.T.
      Obstetric technologies: what determines clinical acceptance or rejection of results of randomized controlled trials?.
      In addition, in the future to avoid being beset by criticism that EFM and STAN do not improve long-term outcomes, like cerebral palsy or neonatal mortality, RCTs, at a scale unknown to us thus far, must be undertaken. Alternatively, we could accept evidence from the population-based study with external validity, like our current study.

      Conclusion

      In conclusion, our data suggests that in the United States, in real life practice, the use of EFM increases operative delivery, while decreasing early neonatal mortality-and therefore infant mortality-and also decreasing neonatal morbidity. The benefits of EFM are gestational age dependent with the highest impact demonstrated in the preterm fetus. Although awaiting future RCTs to address the role of EFM in conjunction with STAN, in defining long-term neonatal outcomes, attempts should be made to minimize unnecessary interventions.

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      Linked Article

      • Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States
        American Journal of Obstetrics & GynecologyVol. 206Issue 1
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          The Journal recently published an article suggesting a causal association between electronic fetal monitoring (EFM) and decreased infant mortality.1 We have strong reservations regarding the ability of that paper to offer guidance regarding the effectiveness of EFM because it is inappropriate to use vital statistics data to make the leap from statistical association to causation.
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      • Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States
        American Journal of Obstetrics & GynecologyVol. 206Issue 2
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          Chen et al1 found decreased early neonatal mortality rates among infants who were recorded on birth certificates as having had electronic fetal monitoring (EFM) during labor compared with those who did not have EFM recorded on the birth certificate. The authors invoke the large size of this study as a major strength over RCTs comparing EFM and intermittent auscultation (IA). At first glance, this observational study would seem to affirm widely supported, validated recommendations to monitor the fetal heart rate during labor,2 but on closer examination many of its findings may be substantially biased.
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