O. Yagel

Sonographic large fetal head circumference and risk of cesarean delivery

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 patients 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.

OC13.02: Fetal head circumference to predict delivery mode: a pilot study

Objectives: Fetal macrosomia is a perennial obstetric management problem. Macrosomia assessment is based mostly on clinically or sonographically EFW. We explored the impact of head circumference (HC) on obstetric outcomes including delivery mode and maternal and neonatal complications, as compared to birth weight, in order to improve the management of ‘‘big babies.’’ Methods: In several parallel cohort studies based on over 120,000 term singleton deliveries we analysed the association of HC with unplanned Caesarean delivery [UCD] and vacuum extraction (VE), failed vacuum, prolonged second stage of labour (PSSL), persistent occiput posterior (OP) position at delivery, levator ani avulsion, and neonatal outcomes including Apgar<7, umbilical artery pH≤7.1, and NICU admission. Results: When HC≥95th centile, the risks of PSSL, UCD, VE, failed vacuum, and neonatal complications, are significantly increased. Risk of levator ani avulsion is increased when HC≥90th centile. Results (OR and 95% CI) as compared with high birthweight are summarised in table 1. Conclusions: In several studies we have observed that large HC (≥90th or 95th centile) impacts on length of second stage, delivery mode, maternal pelvic floor trauma, and neonatal complications. OP position at delivery intensifies the effect of large HC. We propose that prelabour counselling and obstetric management take into account head circumference, along with other fetal and maternal parameters.

Higher Rates of Operative Delivery and Maternal and Neonatal Complications in Persistent Occiput Posterior Position with a Large Head Circumference: A Retrospective Cohort Study

Introduction: We investigated whether large head circumference (HC) combined with persistent occiput posterior (OP) position is associated with higher rates of operative delivery and obstetric and neonatal complications than OP deliveries without large HC or in occiput anterior (OA) position. Materials and Methods: Term singleton deliveries in our centers from January 2010 to December 2014, delivered in cephalic OA (n = 41,038) or OP position (n = 1,740), were assessed. We compared delivery modes, maternal and neonatal complications in OA versus OP deliveries, and HC ≥90th centile versus HC <90th centile in persistent OP position. Results: Persistent OP position combined with HC ≥90th centile was associated with higher rates of vacuum extraction and unplanned cesarean delivery than HC <90th centile in OP position (20.1 vs. 17.2%, OR 1.53 [95% CI 0.99-2.36], and 23.4 vs. 9.2%, OR 3.326 [95% CI 2.17-5.11], respectively). Rates of prolonged second stage of labor and neonatal intensive care unit admission were also increased compared to those in either OA position with HC ≥90th centile or OP position with HC <90th centile. Discussion: Large HC combined with OP position is associated with higher rates of operative delivery and prolonged second stage of labor compared to OP delivery with HC <90th centile. HC might be included with other measures to assess women in labor, as it is associated with fetal outcomes in OP deliveries.

OC16.07: Variations between fetal and neonatal head circumference and fetal and neonatal weight are size-dependent

regression performed, to identify relation of AOP predicting CD to cervical dilatation. Results: 119 women were included in the study. 90(76%) delivered vaginally while 29 had CD (24%). Women undergoing CD had significantly narrower AOP at rest (93 versus 104, P=0.001) and under maternal pushing (102 versus 118, P<0.0001). ROC curve analysis for AOP as a predictor of CD showed AUC of 68% (95 CI 59-77%) for static and 73% (95CI 64-81%) for dynamic assessment. On univariate logistic regression analysis both static AoP (OR 1.04 (95CI 1.01-1.07, P =0.008)) dynamic AoP (1.05 (95CI 1.02-1.08), P =0.0003) were independent predictors of CD from cervical dilatation (OR 1 (95% CI 0.97-1.03), P= 0.8). Conclusions: AoP at rest and on maternal pushing can predict Caesarean delivery in the first stage independently from cervical dilatation.

Vacuum extraction failure is associated with a large head circumference

Abstract Objective: To determine whether large head circumference increases the risk of vacuum extraction failure. Study design: This EMR-based study included all attempted vacuum extractions performed in a tertiary center between January 2010 and June 2015. All term singleton live births were eligible. Cases were divided into four groups: head circumference ≥90th percentile both with birth weight ≥90th percentile and <90th percentile and fetal head circumference <90th percentile with birth weight ≥90th and <90th percentile. Risk of failed vacuum extraction was compared among these groups. Other neonatal and maternal parameters were also evaluated as potential risk factors. Multinomial multivariable regression provided adjusted odds ratio for vacuum extraction failure while controlling for potential confounders. Results: During the study period, 48,007 deliveries met inclusion criteria, of which 3835 had an attempt at vacuum extraction. We identified 215 (5.6%) cases of vacuum extraction failure. The adjusted odds ratios (aOR) for vacuum extraction failure in cases of large fetal head circumference was 2.31 (95%CI, 1.7–3.15, p < .001). Primiparity, prolonged second stage and occipito-posterior presentation were also found to be significant risk factors for failed vacuum extraction. Comments: In this study, we found that large head circumference was associated with vacuum extraction failure rather than high birth weight.

P13.09: Is a prolonged second stage of labour too long?

Objectives: To compare the acceptability of the techniques of vaginal examination (VE) and transperineal ultrasound (USS) techniques (transabdominal (TA) and transperineal (TP)) prior to delivery. Methods: 119 women 24-42 weeks gestation requiring a VE were consented as part of a prospective observational study April 2015-July 2016. The acceptability of both techniques was assessed pre and post examination using the modified Wijma-Delivery Experience Questionnaire, W-DEQ and the effect of Regional Analgesia (RA) was investigated. Experience scores in 6 domains: positive-trust and relax, negative-harmful to baby, worrying, painful, intrusive ranged from 6-36 (6 being most and 36 being least positive). Results: 115 women completed pre-assessment and 104 women completed both pre and post assessment questionnaires. Median age was 31(±5 SD), BMI 25kg/m2 (±4.6 SD), 89% of patients were nulliparous with median gestation 40+2 weeks (r25-42+1). 32% had RA at the time of assessment (91% for delivery). Pre-assessment median experience scores were 15 and 7 respectively (p<0.0001*), post-assessment were 12 versus 6 for VE versus USS respectively (p<0.0001*). The use of RA made no difference to the perceived experience pre-VE (p=0.9*). Post VE, women with RAs considered VEs more acceptable than did those without RA (p=0.0022*). For USS, the use of RA made no difference to the pre and post assessment scores (p=0.5370 vs. p=0.7739*). *Mann Whitney U Test. Conclusions: This is the first study to comprehensively assess positive and negative aspects of the acceptability of VE and intrapartum USS techniques and the impact of RA. USS assessment prior to labour is more acceptable than VE both before and after the examinations. RA did ameliorate the negative experience of the more intrusive VE post assessment but had no effect on the pre and post experience scores of USS implying that without RA, USS is preferred. These findings have implications for women in early labour, without RA, or conditions such as vaginismus or genital mutilation where VE is poorly tolerated.