Advertisement

Sonographic large fetal head circumference and risk of cesarean delivery

Published:January 02, 2018DOI:https://doi.org/10.1016/j.ajog.2017.12.230

      Background

      Persistently high rates of cesarean deliveries are cause for concern for physicians, patients, and health systems. Prelabor assessment might be refined by identifying factors that help predict an individual patient’s risk of cesarean delivery. Such factors may contribute to patient safety and satisfaction as well as health system planning and resource allocation. In an earlier study, neonatal head circumference was shown to be more strongly associated with delivery mode and other outcome measures than neonatal birthweight.

      Objective

      In the present study we aimed to evaluate the association of sonographically measured fetal head circumference measured within 1 week of delivery with delivery mode.

      Study Design

      This was a multicenter electronic medical record-based study of birth outcomes of primiparous women with term (37-42 weeks) singleton fetuses presenting for ultrasound with fetal biometry within 1 week of delivery. Fetal head circumference and estimated fetal weight were correlated with maternal background, obstetric, and neonatal outcome parameters. Elective cesarean deliveries were excluded. Multinomial regression analysis provided adjusted odds ratios for instrumental delivery and unplanned cesarean delivery when the fetal head circumference was ≥35 cm or estimated fetal weight ≥3900 g, while controlling for possible confounders.

      Results

      In all, 11,500 cases were collected; 906 elective cesarean deliveries were excluded. A fetal head circumference ≥35 cm increased the risk for unplanned cesarean delivery: 174 fetuses with fetal head circumference ≥35 cm (32%) were delivered by cesarean, vs 1712 (17%) when fetal head circumference <35 cm (odds ratio, 2.49; 95% confidence interval, 2.04–3.03). A fetal head circumference ≥35 cm increased the risk of instrumental delivery (odds ratio, 1.48; 95% confidence interval, 1.16–1.88), while estimated fetal weight ≥3900 g tended to reduce it (nonsignificant). Multinomial regression analysis showed that fetal head circumference ≥35 cm increased the risk of unplanned cesarean delivery by an adjusted odds ratio of 1.75 (95% confidence interval, 1.4–2.18) controlling for gestational age, fetal gender, and epidural anesthesia. The rate of prolonged second stage of labor was significantly increased when either the fetal head circumference was ≥35 cm or the estimated fetal weight ≥3900 g, from 22.7% in the total cohort to 31.0%. A fetal head circumference ≥35 cm was associated with a higher rate of 5-minute Apgar score ≤7: 9 (1.7%) vs 63 (0.6%) of infants with fetal head circumference <35 cm (P = .01). The rate among fetuses with an estimated fetal weight ≥3900 g was not significantly increased. The rate of admission to the neonatal intensive care unit did not differ among the groups.

      Conclusion

      Sonographic fetal head circumference ≥35 cm, measured within 1 week of delivery, is an independent risk factor for unplanned cesarean delivery but not instrumental delivery. Both fetal head circumference ≥35 cm and estimated fetal weight ≥3900 g significantly increased the risk of a prolonged second stage of labor. Fetal head circumference measurement in the last days before delivery may be an important adjunct to estimated fetal weight in labor management.

      Key words

      Introduction

      The high rates of cesarean delivery, particularly primary cesarean delivery, are a persistent concern for women and their care providers.
      • Simon A.E.
      • Uddin S.G.
      National trends in primary cesarean delivery, labor attempts, and labor success, 1990-2010.
      • American College of Obstetricians and Gynecologists; Society for Maternal-Fetal Medicine
      • et al.
      Safe prevention of the primary cesarean delivery.
      Reduction in these rates is an important goal of professional societies,
      • American College of Obstetricians and Gynecologists; Society for Maternal-Fetal Medicine
      • et al.
      Safe prevention of the primary cesarean delivery.
      to prevent unnecessary interventions and associated morbidity and cost outlay, as well as to prevent an increase in future complications such as placenta accreta
      • Creanga A.A.
      • Bateman B.T.
      • Butwick A.J.
      • et al.
      Morbidity associated with cesarean delivery in the United States: is placenta accreta an increasingly important contributor?.
      • Timor-Tritsch I.E.
      • Monteagudo A.
      Unforeseen consequences of the increasing rate of cesarean deliveries: early placenta accreta and cesarean scar pregnancy. A review.
      and others.
      • Marshall N.E.
      • Fu R.
      • Guise J.M.
      Impact of multiple cesarean deliveries on maternal morbidity: a systematic review.
      Various approaches aimed to decrease cesarean delivery rates have been implemented, with differing degrees of success.
      • Rosenbloom J.I.
      • Stout M.J.
      • Tuuli M.G.
      • et al.
      New labor management guidelines and changes in cesarean delivery patterns.
      • Clark S.L.
      • Belfort M.A.
      • Byrum S.L.
      • Meyers J.A.
      • Perlin J.B.
      Improved outcomes, fewer cesarean deliveries, and reduced litigation: results of a new paradigm in patient safety.
      • Srinivas S.K.
      • Small D.S.
      • Macheras M.
      • Hsu J.Y.
      • Caldwell D.
      • Lorch S.
      Evaluating the impact of the laborist model of obstetric care on maternal and neonatal outcomes.
      • Schuster M.
      • Madueke-Laveaux O.S.
      • Mackeen A.D.
      • Feng W.
      • Paglia M.J.
      The effect of the MFM obesity protocol on cesarean delivery rates.
      • Nicholson J.M.
      • Stenson M.H.
      • Kellar L.C.
      • Caughey A.B.
      • Macones G.A.
      Active management of risk in nulliparous pregnancy at term: association between a higher preventive labor induction rate and improved birth outcomes.
      • Wang C.
      • Wei Y.
      • Zhang X.
      • et al.
      A randomized clinical trial of exercise during pregnancy to prevent gestational diabetes mellitus and improve pregnancy outcome in overweight and obese pregnant women.
      Fetal macrosomia, its management, and sequelae are constants in obstetric practice, as recently reviewed succinctly by Campbell
      • Campbell S.
      Fetal macrosomia: a problem in need of a policy.
      ; estimated fetal weight (EFW) is imprecise,
      • Coomarasamy A.
      • Connock M.
      • Thornton J.
      • Khan K.S.
      Accuracy of ultrasound biometry in the prediction of macrosomia: a systematic quantitative review.
      and overestimation of fetal size may lead to stronger tendency to opt for cesarean delivery for labor arrest.
      • Blackwell S.C.
      • Refuerzo J.
      • Chadha R.
      • Carreno C.A.
      Overestimation of fetal weight by ultrasound: does it influence the likelihood of cesarean delivery for labor arrest?.
      It is the fetal head, however, that is the point of interface between the “passenger” and the “passageway.” Researchers in the fields of anthropology and human evolution have examined the obstetric dilemma of bipedalism and encephalization, ie, the impact of the passage of the large fetal head through the bipedal human pelvis and the risk of fetal-pelvic disproportion.
      • Rosenberg K.
      • Trevathan W.
      Birth, obstetrics and human evolution.
      • Wells J.C.
      Between Scylla and Charybdis: renegotiating resolution of the ‘obstetric dilemma’ in response to ecological change.
      • Wells J.C.
      • DeSilva J.M.
      • Stock J.T.
      The obstetric dilemma: an ancient game of Russian roulette, or a variable dilemma sensitive to ecology?.
      • Wittman A.B.
      • Wall L.L.
      The evolutionary origins of obstructed labor: bipedalism, encephalization, and the human obstetric dilemma.
      • Mitteroecker P.
      • Huttegger S.M.
      • Fischer B.
      • Pavlicev M.
      Cliff-edge model of obstetric selection in humans.
      • Mitteroecker P.
      • Windhager S.
      • Pavlicev M.
      Cliff-edge model predicts intergenerational predisposition to dystocia and cesarean delivery.
      Investigators have proposed a “cliff-edge” model to illustrate the conflict between the evolutionary advantage of a large fetus and the relatively narrow female pelvis.
      • Mitteroecker P.
      • Huttegger S.M.
      • Fischer B.
      • Pavlicev M.
      Cliff-edge model of obstetric selection in humans.
      • Mitteroecker P.
      • Windhager S.
      • Pavlicev M.
      Cliff-edge model predicts intergenerational predisposition to dystocia and cesarean delivery.
      In recent years, we have investigated the impact of fetal anthropomorphic measures on obstetric outcomes, focusing primarily on the fetal head.
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      • Valsky D.V.
      • Lipschuetz M.
      • Bord A.
      • et al.
      Fetal head circumference and length of second stage of labor are risk factors for levator ani muscle injury, diagnosed by 3-dimensional transperineal ultrasound in primiparous women.
      • Valsky D.V.
      • Cohen S.M.
      • Lipschuetz M.
      • et al.
      Third- or fourth-degree intrapartum anal sphincter tears are associated with levator ani avulsion in primiparas.
      We queried how fetal head dimensions might impact the passage of the fetus through the birth canal and affect obstetric outcomes, primarily delivery mode. Our study
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      of postnatally measured head circumference (HC) and birthweight (BW) showed that a large HC was more strongly associated with delivery mode and neonatal complications than a high BW.
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      Multinomial regression showed that infants with HC ≥95th centile combined with BW <95th centile were >3 times more likely to be delivered by unplanned cesarean (adjusted odds ratio [aOR], 3.08; 95% confidence interval [CI], 2.52–3.75) and instrumental delivery (aOR, 3.03; 95% CI, 2.46–3.75) than infants with both HC and BW <95th centile.
      Our findings have been confirmed by others, studying diverse populations.
      • de Vries B.
      • Bryce B.
      • Zandanova T.
      • et al.
      Is neonatal head circumference related to cesarean section for failure to progress?.
      In addition, we
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      and others
      • Ooi P.V.
      • Ramphul M.
      • Said S.
      • Burke G.
      • Kennelly M.M.
      • Murphy D.J.
      Ultrasound assessment of fetal head circumference at the onset of labor as a predictor of operative delivery.
      • Melamed N.
      • Yogev Y.
      • Danon D.
      • Mashiach R.
      • Meizner I.
      • Ben-Haroush A.
      Sonographic estimation of fetal head circumference: how accurate are we?.
      have shown that postnatal measures of HC correlate well with fetal HC (FHC). Therefore, the concept that fetal head dimensions have an impact on the risks of operative delivery and maternal and fetal complications is supported by our findings. We now aimed to examine the association between sonographic FHC measured within 1 week of delivery and delivery mode. Consideration of FHC in addition to EFW could potentially add another layer to evaluation of the suspected macrosomic fetus. This additional information might reassure mothers and their caregivers of the feasibility of a trial of labor and it might also steer caregivers in their choice of intervention, should such become necessary. A combination of parameters may reduce rates of maternal and fetal complications by tailoring management toward interventions where and when they are needed, while helping to avoid unnecessary or inappropriate interventions where possible.

      Materials and Methods

      This is an electronic medical records–based multicenter study performed in 3 tertiary care centers in Israel. Our institutional ethical review boards reviewed and approved the study (0632-15-HMO, 0137-16-SOR, 4466-17-SMC). Data were extracted from deliveries occurring from April 2010 through October 2017 in the 2 campuses of Hadassah-Hebrew University Medical Center in Jerusalem, Soroka University Medical Center in Be'er Sheva, and Chaim Sheba Medical Center in Ramat Gan. Primiparous women with term (37-42 weeks) singleton fetuses who underwent ultrasound with fetal biometry and subsequently delivered within 1 week of the ultrasound scan were included. Populations were mixed high- and low-risk gravidae. Sonographic biometry was performed according to the International Society of Ultrasound in Obstetrics and Gynecology guidelines.
      • Salomon L.J.
      • Alfirevic Z.
      • Berghella V.
      • et al.
      Practice guidelines for performance of the routine mid-trimester fetal ultrasound scan.
      Only the sonographically EFW, calculated with the Hadlock formula, was recorded in the labor ward patient record; midwives and physicians were not aware of the FHC measurements. Elective cesarean deliveries were excluded from analysis. The length of the second stage of labor was defined as prolonged when >3 hours with epidural anesthesia administration and 2 hours without.
      ACOG Committee on Practice Bulletins-Obstetrics
      Operative vaginal delivery. Practice bulletin no. 17. In: Clinical management guidelines for obstetrician and gynecologists.
      Ultrasound reports were extracted from our ultrasound units’ databases and cross-referenced with delivery ward files to obtain obstetric background and outcome data, including maternal demographic parameters, second stage length, and delivery mode, as well as neonatal outcome parameters. Those extracting and analyzing data (M.L., S.M.C., J.B., A.I.) were not involved in patient care; the sonographers and labor ward staff who recorded data in real time at point of care were not aware of the study.
      In a preliminary study, FHC ≥35 cm and EFW ≥3900 g were ascertained as cut-off values above which we observed increased risk of cesarean delivery. An earlier study
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      found that prenatal and neonatal HC correlate strongly, with a steady 1-cm difference, and that a large HC increases risk of operative delivery and neonatal complications in term (37-42 weeks) singletons. The cut-offs investigated here approximate the measurements determined previously.

      Statistical analysis

      Statistical analysis was performed with SPSS 21 for Windows (IBM Corp, Armonk, NY); R software, Version 3.4.1 (R Foundation for Statistical Computing, Vienna, Austria); and Office Excel 2010 (Microsoft, Seattle, WA). Dichotomous variables were compared with the χ2 test or Fisher exact test in cases of small numbers; Mann-Whitney U test was applied to analyze differences in continuous variables.
      Multinomial multivariable regression was used to obtain aOR of the mode of delivery for FHC ≥35 cm or EFW ≥3900 g, with spontaneous vaginal delivery as the reference group, while controlling for maternal age, gestational age at delivery, infant gender, and epidural anesthesia administration. Odds ratios (ORs) and aORs are reported with 95% CI.
      As we showed previously, not all neonates with a large HC had a high EFW, and vice versa.
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      We compared the impact of FHC and EFW in fetuses of different proportions. We constructed a multinomial multivariable regression model for modes of delivery, applying 4 strata of FHC and EFW, where each subgroup included fetuses having none, one, or both of these parameters above the cut-off values of 35 cm and 3900 g, respectively.

      Results

      A total cohort of 11,500 singleton deliveries to nulliparous women with an ultrasound report within 1 week of delivery was collected. After exclusion of elective cesarean deliveries (n = 906, 9.5%), 10,594 remained for analysis.
      Table 1 summarizes the demographic and obstetric background parameters of the study cohort and FHC ≥35 cm and EFW ≥3900 g subgroups. The subgroups did not differ clinically significantly from the cohort in maternal age or gestational age at delivery. The second stage of labor was significantly longer, and was more frequently prolonged beyond the guidelines
      ACOG Committee on Practice Bulletins-Obstetrics
      Operative vaginal delivery. Practice bulletin no. 17. In: Clinical management guidelines for obstetrician and gynecologists.
      for deliveries of fetuses with FHC ≥35 cm and those with EFW ≥3900 g.
      Table 1Demographic and obstetric characteristics of study cohort: ≥35 cm fetal head circumference and ≥3900 g estimated fetal birthweight
      Cohort

      n = 10,594
      Fetal head circumferenceEstimated fetal weight
      <35 cm

      n = 10,050
      ≥35 cm

      n = 544
      P value<3900 g

      n = 9772
      ≥3900 g

      n = 822
      P value
      Comparison of fetal head circumference ≥35 cm and estimated fetal weight ≥3900 g subgroups to cohort and were calculated for χ2 test for dichotomous variables, or Fisher exact test where appropriate, and Mann-Whitney U test for continuous variables
      Maternal age, y, mean (SD)29.7 (5.04)29.7 (5.03)29.03 (5.09).00329.7 (5.04)29.1 (4.91).001
      GA at delivery, wk, mean (SD)39.5 (1.2)39.4 (1.2)40.1 (1.08)<.00139.4 (1.21)40.17 (0.94)<.001
      Infant sex, % male5357 (50.6)4978 (49.5)379 (69.7)<.0014911 (50.3)446 (54.3).030
      Fetal head circumference, cm, mean (SD)33.08 (1.13)32.95 (1.0)35.45 (0.46)<.00133.00 (1.09)34.04 (1.08)<.001
      Estimated fetal weight, g, mean (SD)3330 (414)3307 (406)3761 (320)<.0013268 (368)4063 (140)<.001
      Epidural administration (%)8519 (81.4)8094 (81.5)425 (81.0).817873 (81.6)646 (80.1).35
      Length of second stage, min, mean (SD)114.5 (69)113.3 (69)131.6 (72)<.001113.0 (68)134.1 (71)<.001
      Prolonged second stage
      n = cases for which length of second stage was recorded in medical record.
      (%) n = 7506
      1704 (22.7)1589 (22.2)115 (31.0)<.0011542 (22.0)162 (31.1)<.001
      Apgar ≤7 (%)72 (0.7%)63 (0.6)9 (1.7).0162 (0.6)10 (1.2).08
      NICU admission (%)50 (0.5%)47 (0.5)3 (0.6)143 (0.4)7 (0.8).167
      BPD, biparietal diameter; GA, gestational age; NICU, neonatal intensive care unit; NS, nonsignificant; UCD, unplanned cesarean delivery.
      Lipschuetz et al. Large fetal head and cesarean delivery. Am J Obstet Gynecol 2018.
      a Comparison of fetal head circumference ≥35 cm and estimated fetal weight ≥3900 g subgroups to cohort and were calculated for χ2 test for dichotomous variables, or Fisher exact test where appropriate, and Mann-Whitney U test for continuous variables
      b n = cases for which length of second stage was recorded in medical record.
      Sonographic FHC ≥35 cm and EFW ≥3900 g increased the risk for unplanned cesarean delivery (Table 2). Among fetuses with a FHC ≥35 cm, 174 (32%) were delivered by cesarean, vs 1712 (17%) among fetuses with a FHC <35 cm (OR, 2.49; 95% CI, 1.40–2.18); among those with an EFW ≥3900 g, 295 (36%) were delivered by cesarean, vs 1591 (16%) among fetuses with an EFW <3900 g (OR, 2.90; 95% CI, 2.48–3.39). An EFW ≥3900 g tended to reduce the risk of instrumental delivery (NS), while FHC ≥35 cm increased it (OR, 1.48; 95% CI, 1.16–1.88). Figure 1 shows the proportions of cesarean and instrumental deliveries of fetuses stratified into 10 0.5-cm increments of FHC and 8 200-g increments of EFW. Incremental increase in FHC demonstrates a steady increase in the rate of cesarean delivery, until rising abruptly when FHC >35 cm. As EFW increases, however, the rates of UCD and instrumental delivery remain fairly stable until they diverge sharply between 3800 and 4000 g.
      Table 2Univariate odds ratios and multinomial regression modeled adjusted odds ratios controlling for gestational age at delivery, fetal gender, and epidural anesthesia administration of modes of delivery comparing fetuses with large head circumference or high birthweight to whole cohort (N = 10,594)
      CohortFetal head circumferenceEstimated fetal weight
      <35 cm

      n = 10,050
      ≥35 cm

      n = 544
      OR (95% CI)

      P value
      aOR (95% CI)

      P value
      <3900 g

      n = 9772
      ≥3900 g

      n = 822
      OR (95% CI)aOR (95% CI)

      P value
      Spontaneous vaginal delivery
      Reference category.
      7111 (67%)6832 (68%)279 (51%)6684 (68%)427 (52%)
      Instrumental1597 (15%)1506 (15%)91 (17%)1.48 (1.16–1.88)

      .002
      1.25 (0.97–1.60)

      .086
      1497 (15%)100 (12%)1.05 (0.83–1.30)

      .698
      0.83 (0.65–1.04)

      .111
      Unplanned cesarean1886 (18%)1712 (17%)174 (32%)2.49 (2.04–3.03)

      <.001
      1.75 (1.4–2.18)

      <.001
      1591 (16%)295 (36%)2.90 (2.48–3.39)

      <.001
      2.58 (2.16–3.07)

      <.001
      Elective cesarean deliveries were excluded.
      aOR, adjusted odds ratio; CI, confidence interval; OR, odds ratio.
      Lipschuetz et al. Large fetal head and cesarean delivery. Am J Obstet Gynecol 2018.
      a Reference category.
      Figure thumbnail gr1
      Figure 1Impact of incremental increase in fetal head circumference and estimated fetal weight on delivery mode
      Proportions of cesarean delivery (CD) and instrumental delivery of fetuses stratified into A, 10 0.5-cm subgroups of fetal head circumference (FHC), and B, 8 200-g subgroups of estimated fetal weight (EFW). Top row under x axis represents range of fetal HC (in cm) and fetal EFW (in kg), respectively.
      Lipschuetz et al. Large fetal head and cesarean delivery. Am J Obstet Gynecol 2018.
      Multinomial regression modeling, controlling for gestational age at delivery, fetal gender, and epidural anesthesia, showed that both FHC ≥35 cm and EFW ≥3900 g increased the risk of unplanned cesarean delivery with aORs of 1.75 (95% CI, 1.4–2.18) and 2.58 (95% CI, 2.16–3.07), respectively. The model showed a trend toward increased risk of instrumental delivery when was FHC ≥35 cm, with aOR 1.25 (95% CI, 0.97–1.60).
      Not all fetuses with FHC ≥35 cm have EFW ≥3900 g, and vice versa. Figure 2 shows a Venn diagram illustrating the overlap between the subgroups. Only 186 (1.8%) of the cohort, or 15.8% of the fetuses who had one or the other large parameter, were big in both parameters. To separate the effects of FHC and EFW we stratified our study group to 4 strata according to their FHC and EFW measures. The reference group was composed of fetuses that had FHC <35 cm and EFW <3900 g. Table 3 shows the rates and ORs for delivery modes for the reference stratum vs the 3 big strata: FHC <35 cm and EFW ≥3900 g; FHC ≥35 cm and EFW <3900 g; and FHC ≥35 cm and EFW ≥3900 g. All 3 strata showed significantly increased risk of cesarean delivery, up to OR 4.43, compared to the reference group. Of note is the differential rate of cesarean deliveries in big babies, ie, those with EFW ≥3900 g. When the FHC was <35 cm, the rate of cesarean was about half of that observed in the stratum with both FHC ≥35 cm and EFW ≥3900 g. This can be reassuring for women with big babies contemplating a trial of labor: their risk of unplanned cesarean is less when the FHC is not >35 cm, as opposed to the risk for a fetus that is big in both weight and head dimensions. The risk of instrumental delivery was increased when FHC ≥35 cm and EFW <3900 g (OR, 1.53; 95% CI, 1.14–2.01).
      Figure thumbnail gr2
      Figure 2Not all high EFW fetuses have large FHC, and vice versa
      Venn diagram illustrates frequency of fetal head circumference (FHC) ≥35 cm and estimated fetal weight (EFW) ≥3900 g, and overlap between them. Only 15.8% of fetuses estimated to have either large FHC or high EFW were big in both parameters, comprising 1.8% of fetuses in total cohort.
      Lipschuetz et al. Large fetal head and cesarean delivery. Am J Obstet Gynecol 2018.
      Table 3Rates and odds ratios of delivery modes in 4 subgroups of cohort (N = 10,594)
      Spontaneous vaginal deliveryInstrumentalOR (95% CI)

      P value
      Unplanned cesareanOR (95% CI)

      P value
      HC <35 cm and EFW <3900 g [reference stratum] n = 94146485 (69%)1430 (15%)1499 (16%)
      FHC <35 cm and EFW ≥3900 g, n = 636347 (55%)76 (12%)0.99 (0.77–1.27)

      .959
      213 (33%)2.66 (2.22–3.18)

      <.001
      FHC ≥35 cm and EFW <3900 g, n = 358199 (56%)67 (19%)1.53 (1.14–2.01)

      .004
      92 (26%)2.00 (1.55–2.57)

      <.001
      FHC ≥35 cm and EFW ≥3900 g, n = 18680 (43%)24 (13%)1.36 (0.84–2.12)

      .190
      82 (44%)4.43 (3.24–6.07)

      <.001
      CI, confidence interval; EFW, estimated fetal weight; FHC, fetal head circumference; HC, head circumference; OR, odds ratio.
      Lipschuetz et al. Large fetal head and cesarean delivery. Am J Obstet Gynecol 2018.
      The rates of prolonged second stage of labor were significantly increased in the 3 subgroups as compared to the reference stratum: when FHC <35 cm and EFW <3900 g, a rate of 21.7% was observed, as compared to 30.2% when FHC <35 cm and EFW ≥3900 g (OR, 1.56; 95% CI, 1.25–1.94); 29.6% when FHC ≥35 cm and EFW <3900 g (OR, 1.51; 95% CI, 1.14–1.98); and 34.2% when FHC ≥35 cm and EFW ≥3900 g (OR, 1.87; 95% CI, 1.25–2.75).
      FHC ≥35 cm was also associated with an increased rate of 5-minute Apgar score ≤7 (Table 1): among those with FHC <35 cm, 63 (0.6%) had low 5-minute Apgar score, as compared to 9 (1.7%) infants with FHC ≥35 cm (P = .01). The rate among neonates with EFW ≥3900 g was not significantly increased. The rate of admission to the neonatal intensive care unit was very low overall, and did not differ among the groups.

      Comment

      Principal findings of the study

      FHC ≥35 cm, measured within 1 week of delivery, was an independent risk factor for unplanned cesarean delivery, and showed a nonsignificant trend toward increased risk of instrumental vaginal delivery. EFW ≥3900 g showed a nonsignificant trend toward a reduction in risk of instrumental delivery. The rate of prolonged second stage of labor was significantly increased both when FHC was ≥35 cm and when EFW was ≥3900 g.
      Fetuses with FHC ≥35 cm were significantly more likely to have a 5-minute Apgar score ≤7, while the increase among those with an EFW ≥3900 g was not significant.
      Not all fetuses with a large FHC or a high EFW had both measures exceeding the cut-off. We found that the rate of overlap between FHC ≥35 cm and EFW >3900 g was about 16%; somewhat lower than the overlap we observed between postnatal measures
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      of HC and BW. Stratification of the study group to 4 strata highlighted the differences among them. Fetuses with a FHC ≥35 cm but an EFW <3900 g, were the only subgroup to show a significantly increased risk of instrumental delivery. We observed a differential rate of cesarean deliveries in big babies, those with EFW ≥3900 g, when the FHC was above vs below the 35-cm cut-off. The rate of cesarean when the FHC was <35 cm was about half that observed in the stratum with both a large FHC and a high EFW.

      Clinical significance

      The present study adds to the growing body of evidence showing that the fetal head, as the part directly interfacing with the maternal pelvis, plays a significant role in the progress and outcome of labor. Knowledge of the FHC in the delivery ward has great potential to supplement traditional EFW during prelabor evaluation of big babies. EFW has been shown to be imprecise
      • Campbell S.
      Fetal macrosomia: a problem in need of a policy.
      • Coomarasamy A.
      • Connock M.
      • Thornton J.
      • Khan K.S.
      Accuracy of ultrasound biometry in the prediction of macrosomia: a systematic quantitative review.
      • Pollack R.N.
      • Hauer-Pollack G.
      • Divon M.Y.
      Macrosomia in postdates pregnancies: the accuracy of routine ultrasonographic screening.
      • Hendrix N.W.
      • Grady C.S.
      • Chauhan S.P.
      Clinical vs sonographic estimate of birth weight in term parturients. A randomized clinical trial.
      • Kayem G.
      • Grange G.
      • Breart G.
      • Goffinet F.
      Comparison of fundal height measurement and sonographically measured fetal abdominal circumference in the prediction of high and low birth weight at term.
      in predicting macrosomia. FHC, on the other hand, has been shown to correlate strongly with neonatal HC, with a steady 1-cm difference resulting from differences in method of measurement.
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      • Melamed N.
      • Yogev Y.
      • Danon D.
      • Mashiach R.
      • Meizner I.
      • Ben-Haroush A.
      Sonographic estimation of fetal head circumference: how accurate are we?.
      Combining the FHC and EFW could refine our assessment of individual fetal and maternal risks. Our earlier study
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      showed that big babies (BW ≥95th centile) with HC <95th centile were successfully delivered vaginally more than any other subgroup. Our present findings regarding prelabor FHC measurement could reassure mothers and their caregivers of the feasibility of vaginal delivery of suspected macrosomic fetuses. The added value of FHC in prelabor evaluation may be a reduction in prelabor cesarean deliveries, as individualized management could guide caregivers to avoid unnecessary interventions on the one hand, and choose appropriate, timely interventions, on the other.
      Previous studies, including ours,
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      • Valsky D.V.
      • Lipschuetz M.
      • Bord A.
      • et al.
      Fetal head circumference and length of second stage of labor are risk factors for levator ani muscle injury, diagnosed by 3-dimensional transperineal ultrasound in primiparous women.
      • Valsky D.V.
      • Cohen S.M.
      • Lipschuetz M.
      • et al.
      Third- or fourth-degree intrapartum anal sphincter tears are associated with levator ani avulsion in primiparas.
      • Ooi P.V.
      • Ramphul M.
      • Said S.
      • Burke G.
      • Kennelly M.M.
      • Murphy D.J.
      Ultrasound assessment of fetal head circumference at the onset of labor as a predictor of operative delivery.
      • Aviram A.
      • Yogev Y.
      • Bardin R.
      • Hiersch L.
      • Wiznitzer A.
      • Hadar E.
      Association between sonographic measurement of fetal head circumference and labor outcome.
      • Mujugira A.
      • Osoti A.
      • Deya R.
      • Hawes S.E.
      • Phipps A.I.
      Fetal head circumference, operative delivery, and fetal outcomes: a multi-ethnic population-based cohort study.
      • Elvander C.
      • Hogberg U.
      • Ekeus C.
      The influence of fetal head circumference on labor outcome: a population-based register study.
      • Kennelly M.M.
      • Anjum R.
      • Lyons S.
      • Burke G.
      Postpartum fetal head circumference and its influence on labor duration in nullipara.
      • Hogberg U.
      • Lekas Berg M.
      Prolonged labor attributed to large fetus.
      • Bardin R.
      • Aviram A.
      • Meizner I.
      • et al.
      Association of fetal biparietal diameter with mode of delivery and perinatal outcome.

      Burke N, Burke G, Breathnach F, et al. A fetal head circumference above the 90th centile is a significant risk factor for cesarean delivery and complicated labor: results from the prospective multi-center Genesis study. Am J Obstet Gynecol 2017;214:S197.

      • Burke N.
      • Burke G.
      • Breathnach F.
      • et al.
      Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study.
      have highlighted the impact of head dimensions on obstetric outcomes. Similar to our findings that neonatal HC >95th centile was more strongly associated with operative delivery modes and neonatal complications than newborn weight,
      • Lipschuetz M.
      • Cohen S.M.
      • Ein-Mor E.
      • et al.
      A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
      a large retrospective study of nulliparae found that a neonatal HC ≥37 cm was associated with double the rate of operative delivery and neonatal complications as compared to those with HC of 34 cm.
      • Mujugira A.
      • Osoti A.
      • Deya R.
      • Hawes S.E.
      • Phipps A.I.
      Fetal head circumference, operative delivery, and fetal outcomes: a multi-ethnic population-based cohort study.
      Investigators in Ireland
      • Ooi P.V.
      • Ramphul M.
      • Said S.
      • Burke G.
      • Kennelly M.M.
      • Murphy D.J.
      Ultrasound assessment of fetal head circumference at the onset of labor as a predictor of operative delivery.
      prospectively accrued a small cohort of primiparae and found that a FHC above a cut-off of 35 cm, measured at the onset of labor, was predictive of operative delivery.
      • Ooi P.V.
      • Ramphul M.
      • Said S.
      • Burke G.
      • Kennelly M.M.
      • Murphy D.J.
      Ultrasound assessment of fetal head circumference at the onset of labor as a predictor of operative delivery.
      It is interesting to note that our populations’ cut-off values of 35 cm and the degree of agreement between FHC and neonatal HC were very similar, strengthening the concept that FHC is a useful adjunct to EFW in the labor ward, and that a FHC measurement of 35 cm could be a useful rule of thumb in other populations.
      Both in that study and in ours, the 35-cm cut-off was applicable to all gestational ages studied. Fetal head dimensions obviously increase with gestational age, ie, the 90th centile of FHC steadily increases. The maternal bony pelvis, however, does not. A single cut-off value is applied in EFW: the 4-kg cut-off is not applied differentially according to gestational age and neither are they managed differently. Indeed, in a large study
      • Jolly M.C.
      • Sebire N.J.
      • Harris J.P.
      • Regan L.
      • Robinson S.
      Risk factors for macrosomia and its clinical consequences: a study of 350,311 pregnancies.
      a 4-kg cut-off was shown to predict labor and delivery outcomes better than the 90th centile.
      • Jolly M.C.
      • Sebire N.J.
      • Harris J.P.
      • Regan L.
      • Robinson S.
      Risk factors for macrosomia and its clinical consequences: a study of 350,311 pregnancies.
      Similarly, a FHC ≥35 cm could raise a warning flag in term deliveries of any gestational age.
      A multicenter study in Ireland
      • Burke N.
      • Burke G.
      • Breathnach F.
      • et al.
      Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study.
      applied FHC combined with fetal abdominal circumference and maternal parameters to develop a risk model of cesarean delivery.
      • Burke N.
      • Burke G.
      • Breathnach F.
      • et al.
      Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study.
      The authors found that as FHC and maternal body mass index (and to a lesser degree, abdominal circumference and maternal age) increased, and maternal height decreased, the risk of cesarean delivery increased.
      Two retrospective studies
      • Aviram A.
      • Yogev Y.
      • Bardin R.
      • Hiersch L.
      • Wiznitzer A.
      • Hadar E.
      Association between sonographic measurement of fetal head circumference and labor outcome.
      • Bardin R.
      • Aviram A.
      • Meizner I.
      • et al.
      Association of fetal biparietal diameter with mode of delivery and perinatal outcome.
      investigated FHC >75th centile
      • Aviram A.
      • Yogev Y.
      • Bardin R.
      • Hiersch L.
      • Wiznitzer A.
      • Hadar E.
      Association between sonographic measurement of fetal head circumference and labor outcome.
      (≥341 mm) or fetal biparietal diameter in the highest quartile (≥97 mm).
      • Bardin R.
      • Aviram A.
      • Meizner I.
      • et al.
      Association of fetal biparietal diameter with mode of delivery and perinatal outcome.
      FHC ≥75 centile was shown to increase the risk of operative vaginal delivery for prolonged second stage of labor and neonatal complications,
      • Aviram A.
      • Yogev Y.
      • Bardin R.
      • Hiersch L.
      • Wiznitzer A.
      • Hadar E.
      Association between sonographic measurement of fetal head circumference and labor outcome.
      while a BPD ≥97 mm increased the risk of obstetric interventions but not the risk of neonatal complications.
      • Bardin R.
      • Aviram A.
      • Meizner I.
      • et al.
      Association of fetal biparietal diameter with mode of delivery and perinatal outcome.
      These results are contrary to our findings that a FHC ≥35 cm increased the risk of unplanned cesarean delivery but not of vacuum delivery. This difference may result from differences in study methodology, or from differences in local protocols for vacuum extraction vs cesarean delivery.
      Our results strengthen the premises of evolutionary scientists who point to the discord between the evolutionary advantage of larger fetuses and the relatively narrow bipedal female pelvis, leading to a cliff edge of fetopelvic disproportion.
      • Mitteroecker P.
      • Huttegger S.M.
      • Fischer B.
      • Pavlicev M.
      Cliff-edge model of obstetric selection in humans.
      • Mitteroecker P.
      • Windhager S.
      • Pavlicev M.
      Cliff-edge model predicts intergenerational predisposition to dystocia and cesarean delivery.

      Study strengths and limitations

      The present study is strengthened by its large cohort of some 11,000 deliveries. To our knowledge this is the largest cohort collected to date for this purpose. In addition, combining data from 3 large medical centers with mixed high- and low-risk gravidae and differing obstetric approaches may make these results more representative of the real world, thereby emphasizing their generalizability. Indeed, our 35-cm cut-off was similar to others’ results,
      • Burke N.
      • Burke G.
      • Breathnach F.
      • et al.
      Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study.
      which would tend to support the validity of this measure. Moreover, clinicians were not aware of the FHC measurement during labor, which makes this study more objective regarding its conclusions. However, the retrospective collection of results is still a limitation. The small numbers of neonatal complications in this cohort of term singleton deliveries underscores the necessity of very large study groups to examine the impact of fetal head measurement on maternal and neonatal complications.

      References

        • Simon A.E.
        • Uddin S.G.
        National trends in primary cesarean delivery, labor attempts, and labor success, 1990-2010.
        Am J Obstet Gynecol. 2013; 209: 554.e1-554.e8
        • American College of Obstetricians and Gynecologists; Society for Maternal-Fetal Medicine
        • et al.
        Safe prevention of the primary cesarean delivery.
        Am J Obstet Gynecol. 2014; 210: 179-193
        • Creanga A.A.
        • Bateman B.T.
        • Butwick A.J.
        • et al.
        Morbidity associated with cesarean delivery in the United States: is placenta accreta an increasingly important contributor?.
        Am J Obstet Gynecol. 2015; 213: 384.e1-384.e11
        • Timor-Tritsch I.E.
        • Monteagudo A.
        Unforeseen consequences of the increasing rate of cesarean deliveries: early placenta accreta and cesarean scar pregnancy. A review.
        Am J Obstet Gynecol. 2012; 207: 14-29
        • Marshall N.E.
        • Fu R.
        • Guise J.M.
        Impact of multiple cesarean deliveries on maternal morbidity: a systematic review.
        Am J Obstet Gynecol. 2011; 205: 262.e1-262.e8
        • Rosenbloom J.I.
        • Stout M.J.
        • Tuuli M.G.
        • et al.
        New labor management guidelines and changes in cesarean delivery patterns.
        Am J Obstet Gynecol. 2017; 217: 689.e1-689.e8
        • Clark S.L.
        • Belfort M.A.
        • Byrum S.L.
        • Meyers J.A.
        • Perlin J.B.
        Improved outcomes, fewer cesarean deliveries, and reduced litigation: results of a new paradigm in patient safety.
        Am J Obstet Gynecol. 2008; 199: 105.e1-105.e7
        • Srinivas S.K.
        • Small D.S.
        • Macheras M.
        • Hsu J.Y.
        • Caldwell D.
        • Lorch S.
        Evaluating the impact of the laborist model of obstetric care on maternal and neonatal outcomes.
        Am J Obstet Gynecol. 2016; 215: 770.e1-770.e9
        • Schuster M.
        • Madueke-Laveaux O.S.
        • Mackeen A.D.
        • Feng W.
        • Paglia M.J.
        The effect of the MFM obesity protocol on cesarean delivery rates.
        Am J Obstet Gynecol. 2016; 215: 492.e1-492.e6
        • Nicholson J.M.
        • Stenson M.H.
        • Kellar L.C.
        • Caughey A.B.
        • Macones G.A.
        Active management of risk in nulliparous pregnancy at term: association between a higher preventive labor induction rate and improved birth outcomes.
        Am J Obstet Gynecol. 2009; 200: 254.e1-254.e13
        • Wang C.
        • Wei Y.
        • Zhang X.
        • et al.
        A randomized clinical trial of exercise during pregnancy to prevent gestational diabetes mellitus and improve pregnancy outcome in overweight and obese pregnant women.
        Am J Obstet Gynecol. 2017; 216: 340-351
        • Campbell S.
        Fetal macrosomia: a problem in need of a policy.
        Ultrasound Obstet Gynecol. 2014; 43: 3-10
        • Coomarasamy A.
        • Connock M.
        • Thornton J.
        • Khan K.S.
        Accuracy of ultrasound biometry in the prediction of macrosomia: a systematic quantitative review.
        BJOG. 2005; 112: 1461-1466
        • Blackwell S.C.
        • Refuerzo J.
        • Chadha R.
        • Carreno C.A.
        Overestimation of fetal weight by ultrasound: does it influence the likelihood of cesarean delivery for labor arrest?.
        Am J Obstet Gynecol. 2009; 200: 340.e1-340.e3
        • Rosenberg K.
        • Trevathan W.
        Birth, obstetrics and human evolution.
        BJOG. 2002; 109: 1199-1206
        • Wells J.C.
        Between Scylla and Charybdis: renegotiating resolution of the ‘obstetric dilemma’ in response to ecological change.
        Philos Trans R Soc Lond B Biol Sci. 2015; 370: 20140067
        • Wells J.C.
        • DeSilva J.M.
        • Stock J.T.
        The obstetric dilemma: an ancient game of Russian roulette, or a variable dilemma sensitive to ecology?.
        Am J Phys Anthropol. 2012; 149: 40-71
        • Wittman A.B.
        • Wall L.L.
        The evolutionary origins of obstructed labor: bipedalism, encephalization, and the human obstetric dilemma.
        Obstet Gynecol Surv. 2007; 62: 739-748
        • Mitteroecker P.
        • Huttegger S.M.
        • Fischer B.
        • Pavlicev M.
        Cliff-edge model of obstetric selection in humans.
        Proc Natl Acad Sci U S A. 2016; 113: 14680-14685
        • Mitteroecker P.
        • Windhager S.
        • Pavlicev M.
        Cliff-edge model predicts intergenerational predisposition to dystocia and cesarean delivery.
        Proc Natl Acad Sci U S A. 2017; 114: 11669-11672
        • Lipschuetz M.
        • Cohen S.M.
        • Ein-Mor E.
        • et al.
        A large head circumference is more strongly associated with unplanned cesarean or instrumental delivery and neonatal complications than high birthweight.
        Am J Obstet Gynecol. 2015; 213: 833.e1-833.e12
        • Valsky D.V.
        • Lipschuetz M.
        • Bord A.
        • et al.
        Fetal head circumference and length of second stage of labor are risk factors for levator ani muscle injury, diagnosed by 3-dimensional transperineal ultrasound in primiparous women.
        Am J Obstet Gynecol. 2009; 201: 91.e1-91.e7
        • Valsky D.V.
        • Cohen S.M.
        • Lipschuetz M.
        • et al.
        Third- or fourth-degree intrapartum anal sphincter tears are associated with levator ani avulsion in primiparas.
        J Ultrasound Med. 2016; 35: 709-715
        • de Vries B.
        • Bryce B.
        • Zandanova T.
        • et al.
        Is neonatal head circumference related to cesarean section for failure to progress?.
        Aust N Z J Obstet Gynaecol. 2016; 56: 571-577
        • Ooi P.V.
        • Ramphul M.
        • Said S.
        • Burke G.
        • Kennelly M.M.
        • Murphy D.J.
        Ultrasound assessment of fetal head circumference at the onset of labor as a predictor of operative delivery.
        J Matern Fetal Neonatal Med. 2015; 28: 2182-2186
        • Melamed N.
        • Yogev Y.
        • Danon D.
        • Mashiach R.
        • Meizner I.
        • Ben-Haroush A.
        Sonographic estimation of fetal head circumference: how accurate are we?.
        Ultrasound Obstet Gynecol. 2011; 37: 65-71
        • Salomon L.J.
        • Alfirevic Z.
        • Berghella V.
        • et al.
        Practice guidelines for performance of the routine mid-trimester fetal ultrasound scan.
        Ultrasound Obstet Gynecol. 2011; 37: 116-126
        • ACOG Committee on Practice Bulletins-Obstetrics
        Operative vaginal delivery. Practice bulletin no. 17. In: Clinical management guidelines for obstetrician and gynecologists.
        American College of Obstetricians and Gynecologists, Washington (DC)2000
        • Pollack R.N.
        • Hauer-Pollack G.
        • Divon M.Y.
        Macrosomia in postdates pregnancies: the accuracy of routine ultrasonographic screening.
        Am J Obstet Gynecol. 1992; 167: 7-11
        • Hendrix N.W.
        • Grady C.S.
        • Chauhan S.P.
        Clinical vs sonographic estimate of birth weight in term parturients. A randomized clinical trial.
        J Reprod Med. 2000; 45: 317-322
        • Kayem G.
        • Grange G.
        • Breart G.
        • Goffinet F.
        Comparison of fundal height measurement and sonographically measured fetal abdominal circumference in the prediction of high and low birth weight at term.
        Ultrasound Obstet Gynecol. 2009; 34: 566-571
        • Aviram A.
        • Yogev Y.
        • Bardin R.
        • Hiersch L.
        • Wiznitzer A.
        • Hadar E.
        Association between sonographic measurement of fetal head circumference and labor outcome.
        Int J Gynaecol Obstet. 2016; 132: 72-76
        • Mujugira A.
        • Osoti A.
        • Deya R.
        • Hawes S.E.
        • Phipps A.I.
        Fetal head circumference, operative delivery, and fetal outcomes: a multi-ethnic population-based cohort study.
        BMC Pregnancy Childbirth. 2013; 13: 106
        • Elvander C.
        • Hogberg U.
        • Ekeus C.
        The influence of fetal head circumference on labor outcome: a population-based register study.
        Acta Obstet Gynecol Scand. 2012; 91: 470-475
        • Kennelly M.M.
        • Anjum R.
        • Lyons S.
        • Burke G.
        Postpartum fetal head circumference and its influence on labor duration in nullipara.
        J Obstet Gynaecol. 2003; 23: 496-499
        • Hogberg U.
        • Lekas Berg M.
        Prolonged labor attributed to large fetus.
        Gynecol Obstet Invest. 2000; 49: 160-164
        • Bardin R.
        • Aviram A.
        • Meizner I.
        • et al.
        Association of fetal biparietal diameter with mode of delivery and perinatal outcome.
        Ultrasound Obstet Gynecol. 2016; 47: 217-223
      1. Burke N, Burke G, Breathnach F, et al. A fetal head circumference above the 90th centile is a significant risk factor for cesarean delivery and complicated labor: results from the prospective multi-center Genesis study. Am J Obstet Gynecol 2017;214:S197.

        • Burke N.
        • Burke G.
        • Breathnach F.
        • et al.
        Prediction of cesarean delivery in the term nulliparous woman: results from the prospective, multicenter Genesis study.
        Am J Obstet Gynecol. 2017; 216: 598.e1-598.e11
        • Jolly M.C.
        • Sebire N.J.
        • Harris J.P.
        • Regan L.
        • Robinson S.
        Risk factors for macrosomia and its clinical consequences: a study of 350,311 pregnancies.
        Eur J Obstet Gynecol Reprod Biol. 2003; 111: 9-14