Use of forceps-assisted vaginal delivery among nulliparous pregnant women with obesity was not associated with adverse maternal or neonatal outcomes, according to the findings of a study presented at the 2023 Annual Pregnancy Meeting of the Society for Maternal-Fetal Medicine (SMFM) and simultaneously published in in the American Journal of Obstetrics & Gynecology.¹

A secondary analysis of data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be study was done to determine the outcomes of attempted operative vaginal delivery in nulliparous women with obesity. Out of the 10,038 participants, Grasch et al included 791 women with cephalic liveborn non-anomalous singletons who delivered ≥34 weeks of gestation and had an attempted operative vaginal delivery. BMI of 30 or greater was defined as maternal obesity, while non-obese women had a BMI of less than 30. Out of the 791 participants, 325 had obesity as per this definition at delivery, while 466 did not have obesity.

When the type of operative vaginal delivery attempted as per BMI at delivery was examined, 169 (35.7%) women without obesity had attempted forceps, while 121 (35.9%) women with obesity had attempted forceps. A total of 297 (62.8%) women without obesity had attempted vacuum delivery, while 204 (60.5%) women with obesity had attempted vacuum delivery.

Analysis revealed that operative vaginal delivery failed in 6.8% of attempts, which was the primary study outcome; failure occurred more often among women with obesity compared to those without obesity; 10.1% (n=34) vs 4.2% (n=20), respectively with adjusted odds ratio (aOR) of 2.23. No significant interaction by instrument type was noted. However, an interaction was seen between composite neonatal morbidity (NICU admission, 5 min Apgar <7, need for respiratory support, respiratory distress) and instrument type.

Neonatal morbidity, which was the secondary outcome of the study, was more common after attempted vacuum delivery among infants born to mothers with obesity; 32.7% vs 22.3%, respectively with aOR of 1.61. However, neonatal morbidity was not evident after attempted forceps delivery. “Other adverse outcomes were neither different by obesity status nor had significant interactions with instrument type,” noted the authors.1

This study shows that attempts to perform operative vaginal delivery failed more often among nulliparous women with obesity than those without obesity. Neonatal morbidity was more common in cases of attempted vacuum delivery, but not attempted forceps among infants born to mothers with obesity. Obese women undergoing cesarean section are at higher risk of experiencing complications. These findings may help the clinician to make an informed decision when considering operative vaginal delivery and the type of operative delivery.

Reference

1. Grasch JL, et al. Association of obesity with outcomes of attempted operative vaginal delivery. Am J Obstet Gynecol. 2023 Jan.;228 (1 Suppl): S490. DOI:https://doi.org/10.1016/j.ajog.2022.11.843