# Risk factors for combined vaginal–cesarean delivery in the vertex–vertex twins: a case–control study

## TL;DR

This study finds that gestational diabetes increases the risk of needing a cesarean for the second twin in vertex–vertex twin pregnancies.

## Contribution

The study identifies gestational diabetes as an independent risk factor for combined vaginal–cesarean delivery in vertex–vertex twin pregnancies.

## Key findings

- Gestational diabetes was significantly more common in combined deliveries (31.8% vs. 10.8%).
- Gestational diabetes remained the only independent risk factor after adjustment (OR 4.06).
- Other factors like maternal age and parity did not significantly influence the outcome.

## Abstract

Twin pregnancies pose unique challenges during labor, particularly the risk of cesarean section for the second twin after vaginal delivery of the first—termed a combined vaginal–cesarean delivery. Although nonvertex presentation of the second twin is a recognized risk factor, predictors in vertex–vertex twin pregnancies remain unclear. The objective of this study was to identify maternal, pregnancy-related, intrapartum, and fetal risk factors associated with combined vaginal–cesarean delivery in twin pregnancies with vertex–vertex presentation.

A retrospective single-center case–control study was conducted at Lis Maternity and Women’s Hospital, Tel Aviv Sourasky Medical Center, between 2012 and 2023. The study included women with twin pregnancies in vertex–vertex presentation who attempted vaginal delivery. The case group comprised women who underwent combined vaginal–cesarean delivery (vaginal birth of the first twin followed by cesarean of the second), while controls delivered both twins vaginally. Maternal, pregnancy-related, intrapartum, and fetal variables were analyzed using univariate and multivariable logistic regression models.

Among 503 twin deliveries meeting inclusion criteria, 22 (4.4%) resulted in combined vaginal–cesarean delivery. Maternal characteristics, labor features, and fetal parameters were similar between groups. Gestational diabetes mellitus was significantly more frequent among combined deliveries (31.8% vs. 10.8%; p = 0.009) and remained the only independent risk factor after adjustment (odds ratio 4.06; 95% CI 1.57–10.53; p = 0.004). No other associations were found between the delivery outcome and other factors, including maternal age, parity, previous cesarean delivery, preeclampsia, instrumental delivery of the first twin, gestational age at delivery, and intertwin birthweight discordance.

In vertex–vertex twin pregnancies, successful vaginal delivery is achieved in approximately 95% of cases. Gestational diabetes mellitus independently increases the likelihood of cesarean delivery for the second twin, suggesting a possible metabolic influence on labor dynamics. Optimal glycemic control and vigilant intrapartum management may help minimize cesarean conversions. Larger multicenter studies are warranted to validate these findings and explore the effect of diabetes severity and treatment type.