Ultrasound Obstet Gynecol 2016; 47: 217–223 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/uog.14837
Association of fetal biparietal diameter with mode of delivery and perinatal outcome R. BARDIN, A. AVIRAM, I. MEIZNER, E. ASHWAL, L. HIERSCH, Y. YOGEV and E. HADAR Helen Schneider Hospital for Women, Rabin Medical Center, Petach-Tikva, Israel; The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
K E Y W O R D S: biparietal diameter; BPD; delivery outcome; mode of delivery; neonatal outcome; perinatal outcome
ABSTRACT Objective To determine the association between sonographic assessment of fetal biparietal diameter (BPD) and pregnancy outcome. Methods This was a retrospective cohort study of pregnancies at 37–42 weeks of gestation which had antepartum sonographic measurement of BPD within 7 days before delivery. Eligibility was limited to singleton pregnancies with neither known structural or chromosomal abnormalities nor prelabor Cesarean delivery (CD). The association of BPD with outcome was analyzed using multivariate logistic regression, receiver–operating characteristics curves and stratification according to BPD quartiles. Results In total, 3229 women were eligible for analysis, of whom 2483 (76.9%) had a spontaneous vaginal delivery (SVD), 418 (12.9%) underwent operative vaginal delivery (OVD) and 328 (10.2%) underwent CD. The mean BPD in the obstetric intervention groups (OVD and CD) was significantly higher than that in the SVD group (P < 0.001). After adjusting for confounders, increased BPD was an independent risk factor such that higher values of BPD were associated with progressively higher risk of obstetric intervention (adjusted odds ratio, 1.05 for each 1-mm increase in BPD (95% CI, 1.02–1.09)), but no clear cut-off value for obstetric intervention was found. The fourth quartile group (BPD ≥ 97 mm) was associated with a significantly lower SVD rate (P < 0.001) and higher OVD rate (P = 0.04), relative to the first (BPD 88–90 mm) and second (BPD 91–93 mm) quartile groups, with no apparent adverse impact on immediate neonatal outcome. Conclusions Increased BPD within the week prior to delivery is an independent risk factor such that higher values of BPD are associated with progressively
higher risk of obstetric intervention; however, in our experience, no adverse neonatal outcome resulted from such intervention. Thus, increased BPD should not discourage a trial of vaginal delivery. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
INTRODUCTION Cephalopelvic disproportion (CPD) is a poorly defined clinical diagnosis that is made retrospectively, usually after a trial of vaginal delivery which failed due to labor dystocia. The basic premise underlying the concept of CPD is that protracted or arrested labor results from a mismatch between maternal pelvis and fetal head size1 . Antepartum sonographic fetal biometry may offer a more coherent method for prediction of CPD prelabor than does clinical digital pelvimetry during labor2 – 4 ; the inaccuracy of the latter is well recognized5 . However, estimated fetal weight is the only sonographic prelabor tool that has been evaluated for predicting mode of delivery6,7 . While an association between head circumference and outcome of labor has been evaluated, the current literature relates mainly to postnatal head circumference, which cannot contribute to antenatal counseling; data on the association between antenatal head circumference measured sonographically8,9 (biparietal diameter (BPD)) and labor outcome are scarce. Since the relative size of the BPD and interspinous distance is critical during labor, we aimed to evaluate the association of fetal BPD measured by ultrasound prior to delivery with mode of delivery and perinatal outcome.
METHODS This was a retrospective cohort analysis of all women who delivered in a single tertiary university-affiliated medical center from July 2008 to December 2013. The study
Correspondence to: Dr R. Bardin, Helen Schneider Hospital for Women, Rabin Medical Center, Petach-Tikva 49100, Israel (e-mail: [email protected]) Accepted: 20 February 2015
Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
ORIGINAL PAPER
Bardin et al.
218
was approved by the institutional review board of Rabin Medical Center.
Deliveries in Rabin Medical Center July 2008–December 2013 (n = 44 263)
Study population The population comprised women with singleton pregnancy at 37 + 0 to 41 + 6 weeks’ gestation, in whom sonographic measurements of fetal biometry (including BPD, femur length, head and abdominal circumferences) within 7 days prior to delivery were available. Antenatal care in our population usually takes place outside the hospital at community clinics; it is performed in the hospital for those with no third-trimester ultrasound available or when clinical suspicion necessitates further evaluation, for example due to amniotic fluid disorders or fetal growth abnormalities. Figure 1 summarizes inclusion of our study population. We excluded fetuses or newborns with confirmed genetic or structural anomalies, parturients undergoing primary (non-labor) Cesarean delivery (CD) and those who experienced antepartum fetal death. We also excluded fetuses with BPD in the lowest 10th percentile of our cohort (88 mm) in order to avoid biases regarding suspected or actual intrauterine growth restriction.
Data collection Data were retrieved from maternal and neonatal medical records. The comprehensive computerized databases of the delivery room and ultrasound unit were cross-tabulated using patient identification numbers. Data from the neonatal unit and the neonatal intensive care unit (NICU) were integrated into the delivery room database using the unique admission number assigned to each parturient and her neonate. Demographic, obstetric and neonatal data were assessed, as were sonographic biometric measurements and outcome of labor and delivery.
Definitions Gestational age was determined based on maternally reported last menstrual period and was confirmed by crown–rump length measured at first-trimester sonography. BPD was measured from the outer edge of the near calvaria to the inner edge of the far calvarial wall (outer–inner), at the level of the third ventricle and thalami10 . Birth-weight percentile was calculated using gender-specific local population-based birth-weight curves11 . Macrosomia was defined as birth weight > 4000 g and a large-for-gestational-age (LGA) newborn was defined by a birth weight > 90th percentile for gestational age11 . Minor perineal laceration was defined by a Grade 1 or 2 perineal tear or episiotomy, and obstetric anal sphincter injury syndrome (OASIS) was defined by a Grade 3 or 4 perineal tear. Regarding indications for obstetric intervention, we defined labor dystocia as arrested first stage of labor or prolonged second stage of labor. Arrested first stage of labor was diagnosed when no progress in dilatation was recorded over 4 h of labor despite adequate contractions (defined
Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
Suspected fetal anomaly (n = 5807) n = 38 456 Gestational age
Association of fetal biparietal diameter with mode of delivery and perinatal outcome R. BARDIN, A. AVIRAM, I. MEIZNER, E. ASHWAL, L. HIERSCH, Y. YOGEV and E. HADAR Helen Schneider Hospital for Women, Rabin Medical Center, Petach-Tikva, Israel; The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
K E Y W O R D S: biparietal diameter; BPD; delivery outcome; mode of delivery; neonatal outcome; perinatal outcome
ABSTRACT Objective To determine the association between sonographic assessment of fetal biparietal diameter (BPD) and pregnancy outcome. Methods This was a retrospective cohort study of pregnancies at 37–42 weeks of gestation which had antepartum sonographic measurement of BPD within 7 days before delivery. Eligibility was limited to singleton pregnancies with neither known structural or chromosomal abnormalities nor prelabor Cesarean delivery (CD). The association of BPD with outcome was analyzed using multivariate logistic regression, receiver–operating characteristics curves and stratification according to BPD quartiles. Results In total, 3229 women were eligible for analysis, of whom 2483 (76.9%) had a spontaneous vaginal delivery (SVD), 418 (12.9%) underwent operative vaginal delivery (OVD) and 328 (10.2%) underwent CD. The mean BPD in the obstetric intervention groups (OVD and CD) was significantly higher than that in the SVD group (P < 0.001). After adjusting for confounders, increased BPD was an independent risk factor such that higher values of BPD were associated with progressively higher risk of obstetric intervention (adjusted odds ratio, 1.05 for each 1-mm increase in BPD (95% CI, 1.02–1.09)), but no clear cut-off value for obstetric intervention was found. The fourth quartile group (BPD ≥ 97 mm) was associated with a significantly lower SVD rate (P < 0.001) and higher OVD rate (P = 0.04), relative to the first (BPD 88–90 mm) and second (BPD 91–93 mm) quartile groups, with no apparent adverse impact on immediate neonatal outcome. Conclusions Increased BPD within the week prior to delivery is an independent risk factor such that higher values of BPD are associated with progressively
higher risk of obstetric intervention; however, in our experience, no adverse neonatal outcome resulted from such intervention. Thus, increased BPD should not discourage a trial of vaginal delivery. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
INTRODUCTION Cephalopelvic disproportion (CPD) is a poorly defined clinical diagnosis that is made retrospectively, usually after a trial of vaginal delivery which failed due to labor dystocia. The basic premise underlying the concept of CPD is that protracted or arrested labor results from a mismatch between maternal pelvis and fetal head size1 . Antepartum sonographic fetal biometry may offer a more coherent method for prediction of CPD prelabor than does clinical digital pelvimetry during labor2 – 4 ; the inaccuracy of the latter is well recognized5 . However, estimated fetal weight is the only sonographic prelabor tool that has been evaluated for predicting mode of delivery6,7 . While an association between head circumference and outcome of labor has been evaluated, the current literature relates mainly to postnatal head circumference, which cannot contribute to antenatal counseling; data on the association between antenatal head circumference measured sonographically8,9 (biparietal diameter (BPD)) and labor outcome are scarce. Since the relative size of the BPD and interspinous distance is critical during labor, we aimed to evaluate the association of fetal BPD measured by ultrasound prior to delivery with mode of delivery and perinatal outcome.
METHODS This was a retrospective cohort analysis of all women who delivered in a single tertiary university-affiliated medical center from July 2008 to December 2013. The study
Correspondence to: Dr R. Bardin, Helen Schneider Hospital for Women, Rabin Medical Center, Petach-Tikva 49100, Israel (e-mail: [email protected]) Accepted: 20 February 2015
Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
ORIGINAL PAPER
Bardin et al.
218
was approved by the institutional review board of Rabin Medical Center.
Deliveries in Rabin Medical Center July 2008–December 2013 (n = 44 263)
Study population The population comprised women with singleton pregnancy at 37 + 0 to 41 + 6 weeks’ gestation, in whom sonographic measurements of fetal biometry (including BPD, femur length, head and abdominal circumferences) within 7 days prior to delivery were available. Antenatal care in our population usually takes place outside the hospital at community clinics; it is performed in the hospital for those with no third-trimester ultrasound available or when clinical suspicion necessitates further evaluation, for example due to amniotic fluid disorders or fetal growth abnormalities. Figure 1 summarizes inclusion of our study population. We excluded fetuses or newborns with confirmed genetic or structural anomalies, parturients undergoing primary (non-labor) Cesarean delivery (CD) and those who experienced antepartum fetal death. We also excluded fetuses with BPD in the lowest 10th percentile of our cohort (88 mm) in order to avoid biases regarding suspected or actual intrauterine growth restriction.
Data collection Data were retrieved from maternal and neonatal medical records. The comprehensive computerized databases of the delivery room and ultrasound unit were cross-tabulated using patient identification numbers. Data from the neonatal unit and the neonatal intensive care unit (NICU) were integrated into the delivery room database using the unique admission number assigned to each parturient and her neonate. Demographic, obstetric and neonatal data were assessed, as were sonographic biometric measurements and outcome of labor and delivery.
Definitions Gestational age was determined based on maternally reported last menstrual period and was confirmed by crown–rump length measured at first-trimester sonography. BPD was measured from the outer edge of the near calvaria to the inner edge of the far calvarial wall (outer–inner), at the level of the third ventricle and thalami10 . Birth-weight percentile was calculated using gender-specific local population-based birth-weight curves11 . Macrosomia was defined as birth weight > 4000 g and a large-for-gestational-age (LGA) newborn was defined by a birth weight > 90th percentile for gestational age11 . Minor perineal laceration was defined by a Grade 1 or 2 perineal tear or episiotomy, and obstetric anal sphincter injury syndrome (OASIS) was defined by a Grade 3 or 4 perineal tear. Regarding indications for obstetric intervention, we defined labor dystocia as arrested first stage of labor or prolonged second stage of labor. Arrested first stage of labor was diagnosed when no progress in dilatation was recorded over 4 h of labor despite adequate contractions (defined
Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.
Suspected fetal anomaly (n = 5807) n = 38 456 Gestational age
