(506) Impact of fetal biparietal diameter greater than 10 centimeters on mode of delivery

Thursday, February 9, 2023

4:00 PM – 5:30 PM

Objective: To evaluate the relationship between fetal biparietal diameter (BPD) greater than 10 cm on prenatal ultrasound and likelihood of successful vaginal delivery.

Study Design: This was a secondary analysis of a retrospective cohort of pregnancies resulting in delivery of live singleton fetuses at a single tertiary-care hospital 2007-2019, from which mode of delivery and biometry measurements from ultrasounds performed at 28-42 weeks’ gestation were available. Delivery outcomes of patients with fetal BPD >10cm in the third trimester were compared to those with BPD < 10cm. Generalized linear models were used to evaluate risk of vaginal delivery, adjusting for estimated fetal weight (EFW) percentile and gestational age at the time of ultrasound assessment.

Results: 17,402 pregnancies met inclusion criteria, of which 155 (0.89%) had a BPD >10.0 cm on ultrasound at 28-42 weeks and a known mode of delivery. Vaginal delivery occurred less often (33.93%) in pregnancies with a BPD >10.0 cm compared to those with BPD measurements < 10.0 cm (67.52%, p = < 0.01). However, after controlling for gestational age at ultrasound assessment and calculated EFW percentile, the relationship between vaginal delivery and BPD >10.0 cm was no longer statistically significant (RR 0.71 [95% CI 0.50-1.01], p=0.059).

Conclusion: After adjusting for gestational age at ultrasound assessment and EFW percentile, Pregnancies with an increased fetal BPD >10 cm on third trimester ultrasound were as likely to achieve vaginal birth as those with a BPD < 10cm. This suggests that pregnancies with elevated fetal biparietal diameters should not be discouraged from attempting vaginal birth in absence of other contraindications to a trial of labor.

Primary & Presenting Author(s)

John R. Soehl, MD (he/him/his)
Fellow Physician
Alpert Medical School of Brown University and Women & Infants Hospital of Rhode Island
Providence, Rhode Island, United States

Coauthor(s)

Anna Whelan, MD (she/her/hers)
Fellow
Women & Infants Hospital of Rhode Island, Warren Alpert Medical School of Brown University
Providence, Rhode Island, United States
Lauren Murphy, MD
Women & Infants Hospital of Rhode Island, Warren Alpert Medical School of Brown University
Providence, Rhode Island, United States
ME
Matthew A. Esposito, MD
Women & Infants Hospital of Rhode Island, Warren Alpert Medical School of Brown University
Providence, Rhode Island, United States
Megan G. Lord, MD (she/her/hers)
Maternal Fetal Medicine
Alpert Medical School of Brown University and Women & Infants Hospital of Rhode Island
Providence, Rhode Island, United States