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Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes

      Objective

      The purpose of this study was to assess maternal and perinatal outcomes as a function of second-stage labor duration.

      Study Design

      We assessed outcomes in nulliparous laboring women who were enrolled in a trial of fetal pulse oximetry.

      Results

      Of 5341 participants, 4126 women reached the second stage of labor. As the duration of the second stage increased, spontaneous vaginal delivery rates declined, from 85% when the duration was <1 hour to 9% when it was ≥5 hours. Adverse maternal outcomes that were associated significantly with the duration of the second stage of labor included chorioamnionitis (overall rate, 3.9%), third- or fourth-degree perineal laceration (overall rate, 8.7%), and uterine atony (overall rate, 3.9%). Odds ratios for each additional hour of the second stage of labor ranged from 1.3–1.8. Among individual adverse neonatal outcomes, only admission to a neonatal intensive care unit was associated significantly with second stage duration (odds ratio, 1.4).

      Conclusion

      The second stage of labor does not need to be terminated for duration alone.

      Key words

      Recent studies suggest that, although the duration of the second stage of labor is associated with increased risks of certain adverse maternal outcomes, there is no relationship between the duration of the second stage and adverse neonatal outcomes. However, most studies of this issue are from single centers,
      • Cohen W.R.
      Influence of the duration of second stage labor on perinatal outcome and puerperal morbidity.
      • Moon J.M.
      • Smith C.V.
      • Rayburn W.F.
      Perinatal outcome after a prolonged second stage of labor.
      • Menticoglou S.M.
      • Manning F.
      • Harman C.
      • Morrison I.
      Perinatal outcome in relation to second-stage duration.
      • Janni W.
      • Schiessl B.
      • Peschers U.
      • et al.
      The prognostic impact of a prolonged second stage of labor on maternal and fetal outcome.
      • O'Connell M.P.
      • Hussain J.
      • MacLennan F.A.
      • Lindow S.W.
      Factors associated with a prolonged second state of labour: a case-controlled study of 364 nulliparous labours.
      • Myles T.D.
      • Santolaya J.
      Maternal and neonatal outcomes in patients with a prolonged second stage of labor.
      • Cheng Y.W.
      • Hopkins L.M.
      • Caughey A.B.
      How long is too long: does a prolonged second stage of labor in nulliparous women affect maternal and neonatal outcomes?.
      and all of the studies are based on retrospectively collected data. We therefore took advantage of data that were collected during a randomized clinical trial to assess whether there is a relationship between the duration of the second stage of labor in nulliparous women and adverse maternal or neonatal outcomes using prospectively collected, multicenter data.
      For Editors' Commentary, see Table of Contents
      See related editorial, page 337

      Materials and Methods

      We conducted a secondary analysis of a clinical trial of fetal pulse oximetry at the 14 clinical centers of the National Institute of Child Health and Human Development Maternal Fetal Medicine Units Network. Participants were nulliparous women who were carrying a singleton vertex fetus and who labored spontaneously or were induced at ≥36 weeks gestation.
      • Bloom S.L.
      • Spong C.Y.
      • Thom E.
      • et al.
      Fetal pulse oximetry and cesarean delivery.
      The present analysis was confined to participants who reached the second stage of labor. Exclusion criteria for the trial included maternal fever immediately before randomization and serious medical conditions such as diabetes mellitus. Pregnancy-associated hypertension was not an exclusion criterion. Each participating center had Institutional Review Board approval for the study.
      Maternal and neonatal data were collected by trained research nurses who were present during the labor to manage the fetal oximeter. Duration of the second stage was calculated as the number of minutes from the first cervical examination that revealed full dilation until delivery. Maternal morbidities are limited to diagnoses that were made after the start of the second stage, including chorioamnionitis, which for study purposes required that the clinical diagnosis had been made, the intrapartum temperature reached at least 38°C, and at least 1 of the following criteria was present: uterine tenderness, foul-smelling vaginal discharge or amniotic fluid, or maternal or fetal tachycardia. The study diagnosis of endometritis required a clinical diagnosis and a postpartum temperature of at least 38°C. Other maternal morbidities were defined on the basis of clinical diagnoses. Perineal laceration data were collected only for women who delivered vaginally.
      Brachial plexus injury was confirmed by central review of records and was diagnosed only when the injury was present at neonatal discharge. Other neonatal morbidities were defined on the basis of clinical diagnoses. In the original trial, a composite outcome of serious neonatal morbidity was defined a priori and consisted of any of the following criteria: a 5-minute Apgar score <4, an umbilical artery pH value <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours.
      The second stage of labor was analyzed both as a continuous and as a dichotomous variable: <3 hours vs ≥3 hours. The division at 3 hours was based on the conventional threshold for defining a prolonged second stage of labor in a nulliparous woman who received epidural analgesia.
      American College of Obstetricians and Gynecologists
      Dystocia and augmentation of labor: ACOG practice bulletin, no. 49.
      Associations between duration of the second stage and the various maternal and neonatal outcomes were analyzed with the use of logistic regression for the continuous duration and chi-square or Fisher's exact test for the dichotomous measure. Logistic regression models for both the continuous and dichotomous measures were used to adjust for mode of delivery (spontaneous, operative vaginal, and cesarean). Additional models that were adjusted for maternal body mass index at delivery and duration of the first stage of labor were analyzed when the outcomes were frequent enough to support valid logistic regressions.
      Because of the infrequency of brachial plexus injury, sepsis, and low 5-minute Apgar score, exact logistic regression was used for these outcomes. All reported probability values were 2-sided, and a probability value of < .05 was considered significant. No adjustments were made for multiple comparisons. SAS software (SAS Institute, Inc, Cary, NC) and LogXact software (Cytel Software Corp, Cambridge, MA) were used for analysis.

      Results

      Of 5341 pregnant women who were enrolled in the clinical trial from May 2002 to February 2005, 4126 women (77%) reached the second stage of labor and with their neonates constituted the study cohort (Table 1). There was no observed effect of the original clinical trial exposure groups (fetal pulse oximetry or not) on either the duration of the second stage or the maternal and neonatal outcomes of interest (data not shown). Therefore, all data from these patients were analyzed independent of fetal pulse oximetry use. As the duration of the second stage increased, spontaneous vaginal delivery rates declined, from 85.2% of those women who delivered with <1 hour in the second stage down to 8.7% of those women who remained in the second stage for ≥5 hours (Table 2).
      TABLE 1Maternal and neonatal characteristics and outcomes
      CharacteristicMeasure
      Maternal
       Age, y
      Data are presented as mean ± SD;
      23.3 ± 5.4
       Race, n (%)
        Black1217 (29.5%)
        White2196 (53.2%)
        Asian58 (1.4%)
        Other655 (15.9%)
       Body mass index, kg/m2,
      Data are presented as mean ± SD;
        Prepregnancy25.0 ± 5.8
        Delivery31.0 ± 6.0
       Ethnic group, n (%)
        Hispanic or Latino1010 (24.5)
        Not Hispanic or Latino3116 (75.5)
       Gestational age, wk
      Data are presented as mean ± SD;
      39.7 ± 1.3
       Type of labor, n (%)
        Spontaneous2535 (61.4)
        Induced1591 (38.6)
       Use of oxytocin, n (%)3592 (87.1)
       Use of epidural analgesia, n (%)3916 (94.9)
       Duration of 1st stage of labor, h
      Data are presented as mean ± SD;
      13.6 ± 7.1
       Type of delivery, n (%)
        Spontaneous3054 (74.0)
        Operative vaginal765 (18.5)
        Cesarean307 (7.4)
       Chorioamnionitis, n (%)
      excludes 246 women who were diagnosed with chorioamnionitis in the first stage;
      151 (3.9)
       Third- or fourth-degree perineal laceration, n (%)
      vaginal deliveries only;
      332 (8.7)
       Endometritis, n (%)121 (2.9)
       Uterine atony, n (%)160 (3.9)
       Blood transfusion, n (%)36 (0.9)
      Neonatal
       Birthweight, g
      Data are presented as mean ± SD;
      3335 ± 451
       Five-minute Apgar score <4, n (%)3 (0.1)
       Umbilical artery pH <7.0, n (%)
      values available for 3524 fetuses;
      16 (0.5)
       Intubation in delivery room, n (%)20 (0.5)
       Neonatal intensive care admission, n (%)181 (4.4)
       Sepsis, n (%)6 (0.1)
       Brachial plexus injury, n (%)11 (0.3)
       Composite, n (%)
      any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours.
      104 (2.5)
      Rouse. Duration of 2nd-stage of labor in nulliparous women. Am J Obstet Gynecol 2009.
      a Data are presented as mean ± SD;
      b excludes 246 women who were diagnosed with chorioamnionitis in the first stage;
      c vaginal deliveries only;
      d values available for 3524 fetuses;
      e any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours.
      TABLE 2Delivery mode and adverse outcomes by duration of the second stage
      Variable<1 h (n = 1901)1 to <2 h (n = 1251)2 to <3 h (n = 614)3 to <4 h (n = 217)4 to <5 h (n = 97)≥5 h (n = 46)Unadjusted odds ratio (95% CI)Adjusted odds ratio (95% CI)
      For each additional hour of the second stage, adjusted for mode of delivery;
      Delivery mode, n (%)
      P <.01;
       Spontaneous1620 (85.2)984 (78.7)363 (59.1)59 (27.2)24 (24.7)4 (8.7)
       Operative vaginal254 (13.4)226 (18.1)173 (28.2)75 (34.6)27 (27.8)10 (21.7)
       Cesarean27 (1.4)41 (3.3)78 (12.7)83 (38.3)46 (47.4)32 (69.6)
      Maternal outcome, n (%)
       Chorioamnionitis20 (1.1)49 (4.2)41 (7.1)29 (14.8)9 (10.6)3 (6.5)1.68 (1.51–1.87)1.60 (1.40–1.83)
       Third- or fourth-degree perineal laceration96 (5.1)101 (8.4)74 (13.8)45 (33.6)12 (23.5)4 (28.6)1.80 (1.62–1.99)1.44 (1.29–1.60)
       Endometritis51 (2.7)33 (2.6)15 (2.4)13 (6.0)2 (2.1)7 (15.2)1.25 (1.09–1.43)1.07 (0.90–1.26)
       Uterine atony57 (3.0)45 (3.6)30 (4.9)17 (7.8)7 (7.2)4 (8.7)1.29 (1.15–1.45)1.31 (1.14–1.51)
       Blood transfusion11 (0.6)12 (1.0)6 (1.0)4 (1.8)1 (1.0)2 (4.3)1.38 (1.11–1.72)1.30 (0.99–1.71)
      Neonatal outcome, n (%)
       Five-minute Apgar score <402 (0.2)1 (0.2)0001.34 (0.62–2.88)1.05 (0.34–2.46)
       Umbilical artery pH <7.04 (0.2)6 (0.6)4 (0.8)1 (0.5)1 (1.2)01.30 (0.91–1.87)0.98 (0.63–1.53)
       Intubation in delivery room7 (0.4)7 (0.6)5 (0.8)01 (1.0)01.14 (0.80–1.62)0.99 (0.65–1.51)
       Neonatal intensive care61 (3.2)62 (5.0)29 (4.7)15 (6.9)9 (9.3)5 (10.9)1.27 (1.14–1.42)1.13 (0.98–1.29)
       Sepsis2 (0.1)3 (0.2)1 (0.2)0001.04 (0.52–2.10)0.88 (0.38–2.03)
       Brachial plexus injury3 (0.2)2 (0.2)4 (0.7)1 (0.5)1 (1.0)01.41 (0.96–2.06)1.78 (1.08–2.78)
       Composite
      any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours
      33 (1.7)36 (2.9)19 (3.1)10 (4.6)4 (4.1)2 (4.4)1.25 (1.08–1.45)1.09 (0.91–1.30)
      CI, confidence interval.
      Rouse. Duration of 2nd-stage of labor in nulliparous women. Am J Obstet Gynecol 2009.
      a For each additional hour of the second stage, adjusted for mode of delivery;
      b P <.01;
      c any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours
      In unadjusted analyses, several adverse maternal outcomes were associated significantly with the duration of the second stage, including chorioamnionitis, endometritis, 3rd- or fourth-degree perineal laceration, uterine atony, and blood transfusion (Table 2). After adjustment for mode of delivery, the association with endometritis and blood transfusion was no longer significant (Table 2). There were no stillbirths or neonatal deaths and 1 case of neonatal hypoxic ischemic encephalopathy (in this case the duration of the second stage was 2 hours, 11 minutes).
      Without adjustment for mode of delivery, admission to a neonatal intensive care unit and the composite of serious morbidities were the only 2 neonatal morbidities that were associated significantly with second-stage duration (Table 2). Admission to a neonatal intensive care unit for at least 48 hours is alone responsible for 62% of the neonatal composite (n = 64 infants); when limited to the remaining components, the composite of morbidities is no longer associated with second-stage duration. After adjustment for mode of delivery, only brachial plexus injury that was present at discharge was associated with second-stage duration (Table 2). The individual cases of brachial plexus injury are described in Table 3.
      TABLE 3Selected characteristics of pregnancies that were complicated by brachial plexus injury
      Duration of the second stage of labor, hBirthweight, gMethod of deliveryStation at forceps
      On a scale of 0-5 cm.
      0.23000Forceps+2
      0.43220Spontaneous
      0.82155Forceps+2
      1.33535Spontaneous
      1.44790Spontaneous
      2.14110Spontaneous
      2.23800Spontaneous
      2.24307Spontaneous
      2.63280Spontaneous
      3.83135Forceps+2
      4.94460Spontaneous
      Rouse. Duration of 2nd-stage of labor in nulliparous women. Am J Obstet Gynecol 2009.
      a On a scale of 0-5 cm.
      The second stage of labor lasted at least 3 hours in 360 women (9% of the cohort). In these women, rates of spontaneous vaginal delivery were significantly lower and rates of operative vaginal and cesarean delivery were higher than in women in whom the second stage lasted <3 hours. Even so, most of the 360 women (55%) with a second stage of at least 3 hours delivered vaginally. Sixty-one percent of cesarean deliveries (n = 89) with a second stage of <3 hours were performed for dystocia vs 93% (n = 149) when the second stage was longer.
      In unadjusted analyses, second-stage duration of at least 3 hours was associated with significantly higher rates of chorioamnionitis, endometritis, third- or fourth-degree perineal lacerations, uterine atony, and blood transfusion (Table 4). After adjustment for mode of delivery, the association with endometritis and blood transfusion was no longer significant (Table 4). Without adjustment for mode of delivery, admission to a neonatal intensive care unit and the composite of serious morbidities were the only 2 neonatal morbidities that were associated significantly with a second-stage duration of at least 3 hours (Table 4). However, after adjustment for mode of delivery, neonatal outcomes did not differ significantly between the patients with a second stage at <3 vs ≥3 hours. Outcomes stratified by mode of delivery and duration of second stage (<3 or ≥3 hours) are presented in Table 5. Additional regression analyses were performed that included body mass index at delivery and duration of the first stage of labor; however, the results were essentially identical (data not shown).
      TABLE 4Second-stage duration and outcomes categorized by duration < or ≥3 hours
      Variable<3 h (n = 3766)≥3 h (n = 360)P value (unadjusted)P value (adjusted)
      Adjusted for mode of delivery;
      Delivery mode, n (%)< .01
       Spontaneous2967 (78.8)87 (24.2)
       Operative vaginal653 (17.3)112 (31.1)
       Cesarean146 (3.9)161 (44.7)
      Maternal outcome, n (%)
       Chorioamnionitis110 (3.1)41 (12.5)< .01< .01
       Third- or fourth-degree perineal laceration
      vaginal deliveries only;
      271 (7.5)61 (30.7)< .01< .01
       Endometritis99 (2.6)22 (6.1)< .01.20
       Uterine atony132 (3.5)28 (7.8)< .01< .01
       Blood transfusion29 (0.8)7 (1.9).03.24
      Neonatal outcome, n (%)
       Five-minute Apgar score <43 (0.1)01.00.90
       Umbilical artery pH < 7.014 (0.4)2 (0.7).64.50
       Intubation in delivery room19 (0.5)1 (0.3)1.00.23
       Neonatal intensive care152 (4.0)29 (8.1)< .01.25
       Sepsis6 (0.2)01.00.72
       Brachial plexus injury9 (0.2)2 (0.6).25.27
       Composite
      any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours
      88 (2.3)16 (4.4).01.69
      Rouse. Duration of 2nd-stage of labor in nulliparous women. Am J Obstet Gynecol 2009.
      a Adjusted for mode of delivery;
      b vaginal deliveries only;
      c any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours
      TABLE 5Outcomes stratified by mode of delivery and second stage duration < or ≥3 hours
      VariableDelivery mode
      VaginalCesarean
      <3 h (n = 3620)≥3 h (n = 199)P value<3 h (n = 146)≥3 h (n = 161)P value
      Maternal outcome, n (%)
       Chorioamnionitis101 (3.0)21 (11.4)< .019 (6.8)20 (14.0).05
       Third- or fourth-degree perineal laceration271 (7.5)61 (30.7)< .01
       Endometritis87 (2.4)9 (4.5).0612 (8.2)13 (8.1).96
       Uterine atony124 (3.4)17 (8.5)< .018 (5.5)11 (6.8).62
       Blood transfusion26 (0.7)4 (2.0).073 (2.1)3 (1.9)1.00
      Neonatal outcome, n (%)
       5-minute Apgar score <42 (0.1)01.001 (0.7)0.48
       Umbilical artery pH <7.011 (0.4)1 (0.6).473 (2.3)1 (0.8).62
       Intubation in delivery room16 (0.4)1 (0.5).603 (2.1)0.11
       Neonatal intensive care140 (3.9)14 (7.0).0312 (8.2)15 (9.3).73
       Sepsis5 (0.1)01.001 (0.7)0.48
       Brachial plexus injury9 (0.2)2 (1.0).1100
       Composite
      Any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours
      79 (2.2)8 (4.0).139 (6.2)8 (5.0).65
      Rouse. Duration of 2nd-stage of labor in nulliparous women. Am J Obstet Gynecol 2009.
      a Any of the following occurrences: a 5-minute Apgar score <4, an umbilical artery pH <7.0, seizures, intubation in the delivery room, stillbirth, neonatal death, or admission to a neonatal intensive care unit for >48 hours

      Comment

      These data, which were collected prospectively from 14 centers, reaffirm that, with current labor management practices, the duration of the second stage of labor is associated principally with adverse maternal as opposed to adverse neonatal outcomes. Without adjustment for mode of delivery, of the several individual adverse neonatal outcomes that we examined, only 1, admission to a neonatal intensive care unit, correlated with second stage duration, and it per se is not strictly a true morbidity. Likewise, the composite outcome of serious neonatal morbidity was associated significantly with second-stage duration, but the neonatal intensive care unit admission component comprised 62% of this composite outcome. After we controlled for mode of delivery, only 1 adverse neonatal outcome; brachial plexus injury that was present at discharge, correlated with second-stage duration, and the absolute risk of this outcome was low (3/1000).
      Cohen,
      • Cohen W.R.
      Influence of the duration of second stage labor on perinatal outcome and puerperal morbidity.
      in a study of 4403 nulliparous women, was the first to observe that, although certain maternal morbidities (specifically postpartum hemorrhage and fever) were increased when the second stage of labor was prolonged, neither 5-minute Apgar scores nor perinatal death was related to second-stage duration. Saunders et al
      • Saunders N.S.G.
      • Paterson C.M.
      • Wadsworth J.
      Neonatal and maternal morbidity in relation to the length of the second stage of labour.
      came to a similar conclusion in their retrospective review of a regional obstetric database. Among 25,069 term deliveries, maternal infection and postpartum hemorrhage were related to the duration of the second stage, but neonatal condition (as reflected by low Apgar scores or admission to a special care nursery) was not. Presumably because relatively few women in their cohort had second-stage durations that exceeded 3 hours, they limited their conclusions to durations that did not exceed this threshold.
      Menticoglou et al
      • Menticoglou S.M.
      • Manning F.
      • Harman C.
      • Morrison I.
      Perinatal outcome in relation to second-stage duration.
      extended the work of Cohen
      • Cohen W.R.
      Influence of the duration of second stage labor on perinatal outcome and puerperal morbidity.
      and Saunders et al
      • Saunders N.S.G.
      • Paterson C.M.
      • Wadsworth J.
      Neonatal and maternal morbidity in relation to the length of the second stage of labour.
      when they reported that, among 6041 nulliparous women, the second stage exceeded 3 hours in 11% and 5 hours in 3%. They found no relationship in their cohort of second-stage duration and low 5-minute Apgar score, neonatal seizures, or neonatal intensive care unit admission. Moreover, 1 in 4 women who were still undelivered after 4 hours in the second stage achieved vaginal delivery in the next hour.
      Janni et al
      • Janni W.
      • Schiessl B.
      • Peschers U.
      • et al.
      The prognostic impact of a prolonged second stage of labor on maternal and fetal outcome.
      reported that the duration of the second stage exceeded 4 hours in 4% of 1457 women, and that second-stage duration bore no relationship to neonatal outcome. Their group did observe that the rate of third-degree perineal lacerations increased as the second stage lengthened. For example, when the second stage was <2 hours, the rate of such tears was 3%, whereas it was 11% when the second stage lasted from 3-4 hours. More recently, Myles and Santolaya
      • Myles T.D.
      • Santolaya J.
      Maternal and neonatal outcomes in patients with a prolonged second stage of labor.
      and Cheng et al
      • Cheng Y.W.
      • Hopkins L.M.
      • Caughey A.B.
      How long is too long: does a prolonged second stage of labor in nulliparous women affect maternal and neonatal outcomes?.
      have reported similar maternal and neonatal outcomes in relationship to second-stage duration. Our study thus is consistent with previous findings.
      The strengths of our data are that they were accrued prospectively, reflect practice patterns and outcomes from 14 centers, and were collected by research nurses who were present during the second stage of labor and delivery. A weakness of our data includes the fact that second-stage labor management was not standardized, which somewhat limits the value of the causal implications of the data. The complications that we observed in association with second-stage duration may not be due per se to duration, or at least duration alone. Similarly, for several of the complications, our study design does not allow us to say that the complications would have been avoided if the second stage had been terminated sooner. Another potential weakness is that, even with a sample size of >4000 women, our statistical power to detect an increased risk of several complications in association with the duration of the second stage was low. Finally, because 95% of women in the study cohort received epidural analgesia, our findings should not be generalized to women who labor without such analgesia.
      Although we did not collect information on shoulder dystocia, we did collect information on the often-associated and more meaningful outcome of brachial plexus injury. By logistic regression analysis, each additional hour in the second stage of labor significantly increased the risk of this outcome by approximately 80%. We caution, however, that this risk estimate is modeled and based on only 11 cases; therefore, the 95% confidence interval is wide and consistent with a risk increase of as little as 10% or as great as 280%. Moreover, in only 2 of the 11 cases was the duration of the second stage ≥3 hours, and in only 4 cases was the birthweight at least 4000 g. Finally, we did not follow the neonates beyond discharge, which is important, because as many as 90% of brachial plexus injuries resolve spontaneously without sequelae.
      • Rouse D.J.
      • Owen J.
      • Goldenberg R.L.
      • Cliver S.P.
      The effectiveness and costs of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound.
      Thus, the clinical implications of this association are unclear.
      In infants who are delivered vaginally, the risk of brachial plexus injury is increased at higher birthweights.
      • Rouse D.J.
      • Owen J.
      • Goldenberg R.L.
      • Cliver S.P.
      The effectiveness and costs of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound.
      However, for 2 reasons, 1 statistical and 1 conceptual, we did not adjust for birthweight in our regression models. First, the infrequency of brachial plexus injury rendered such adjustment statistically unreliable. Second, birthweight can only be estimated before delivery; incorporation of such estimates into clinical management strategies is generally unrewarding,
      • Rouse D.J.
      • Owen J.
      • Goldenberg R.L.
      • Cliver S.P.
      The effectiveness and costs of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound.
      especially if, as in this study, most of the brachial plexus injuries occurred in babies with birthweights of <4000 g.
      Our data should aid in counseling and in the management of the second stage of labor. They support that extending the duration of the second stage of labor will allow some women to achieve vaginal delivery successfully, even those few women in whom the second stage has lasted 5 hours. These vaginal deliveries, however, have a cost that includes higher rates of significant perineal trauma, infectious morbidity, and uterine atony. Some women and their caregivers will find these tradeoffs in attempting to avoid cesarean delivery acceptable, and some will not. The only associated downsides for the fetus to a longer second stage of labor are a higher, but still low, rate of admission to a neonatal intensive care unit and, when adjustment is made for mode of delivery, an increased relative, but still low absolute, risk of brachial plexus injury Again, how these risks are perceived and acted on is likely to vary substantially.

      Acknowledgments

      The authors wish to acknowledge subcommittee members who contributed as follows: Kenneth J. Leveno, MD (protocol development and oversight); Elizabeth Thom, PhD (protocol/data management and statistical analysis); Allison Northen, RN (protocol development and coordination between clinical research centers); and Donald McIntire, PhD (study design).
      In addition to the authors, other members of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network are as follows: University of Alabama at Birmingham, A. Northen, K. Bailey, J. Grant, S. Tate, T. Hill-Webb; Brown University, J. Tillinghast, D. Allard, P. Breault, N. Connolly, J. Silva; Case Western University, C. Milluzzi, C. Heggie, H. Ehrenberg, B. Stetzer; Columbia University, V. Pemberton, S. Bousleiman, H. Husami, V. Carmona, S. South; Drexel University, M. Talucci, M. Pollock, M. Sherman, C. Tocci, E. Seltzer; University of North Carolina, S. Brody, J. Granados, K. Clark, J. Mitchell, K. Dorman; Northwestern University, G. Mallett, N. Cengic, M. Huntley, T. Triplett; The Ohio State University, F. Johnson, S. Fyffe, M. Landon; University of Pittsburgh, M. Cotroneo, M. Luce, H. Birkland, M. Bickus, L. Creswell-Hartman; The University of Texas Health Science Center at Houston, M.C. Day, F. Ortiz, B. Figueroa, S. Shaunfield, M. Messer; University of Texas Southwestern Medical Center, J. McCampbell, L. Moseley; University of Utah, K. Anderson, B. Oshiro (McKay-Dee Hospital), F. Porter (Intermountain Healthcare), K. Jolley, A. Guzman; Wake Forest University Health Sciences, M. Swain, J. Chilton, C. Leftwich, W. Davido, K. Johnson; Wayne State University, G. Norman, B. Steffy, C. Sudz, S. Blackwell; The George Washington University Biostatistics Center, E.A. Thom, A. Swanson, F. Galbis-Reig, L. Leuchtenburg; Eunice Kennedy Shriver National Institute of Child Health and Human Development, S. Pagliaro, K. Howell.

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      Linked Article

      • Is there an upper time limit for the management of the second stage of labor?
        American Journal of Obstetrics & GynecologyVol. 201Issue 4
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          The epidemiology of the length of labor was notoriously reported by Emmanuel Friedman1,2 in several landmark articles >50 years ago. These studies changed modern obstetrics; most specifically, they led to specific normative guidelines on the length of the first and second stages of labor. These normative guidelines generally have become prescriptive and have led to operative deliveries if the length of labor crosses some specific time threshold. However, more recently, a variety of authors have challenged this paradigm for both the first and second stages of labor.
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