The association between low birth weight and outcomes of vacuum assisted vaginal delivery

It is often hypothesized that poor neonatal outcomes are more frequently observed in low birth weight (LBW) neonates following vacuum assisted vaginal delivery (VAVD). We sought to assess the association between low birth weight (< 2500 g) and neonatal outcomes, following vacuum extraction.

This was a retrospective cohort study, including 1085 deliveries in a tertiary medical center between 2003 and 2015. Maternal and neonatal outcomes, including birth trauma related complications, were compared between women with singleton pregnancies beyond 34 weeks' gestation and fetal weight < 2500 g who were delivered by vacuum extraction (n=345) and a control group (n=740) with fetal weight ≥ 2500 g, matched in maternal age, parity and gestational week.

During the study period, 370 women met the inclusion criteria for the study group, with 25 cases eventually excluded due to missing neonatal birth trauma related data. 740 patients were included in the matched control group. Induction of labor and non-reassuring fetal heart rate as an indication for VAVD were more prevalent in the LBW group. The composite birth trauma related adverse outcome was higher in the control group (9.1 % vs. 4.4 %, p = 0.008), mainly due to increased rate of cephalohematoma in this group (6.8 % vs. 2.9 %, p = 0.01). All other adverse neonatal outcomes rates did not differ between the groups. Women in the control group were more prone to post-partum hemorrhage (p < 0.001), had more episiotomies (p = 0.004) and a higher failed VAVD rate (11.4 % vs. 2.6 %, p < 0.001), leading to emergency cesarean delivery. A sub-group analysis of failed VAVD did not reveal a difference in neonatal complications between the LBW and the control group.

Neonatal birth trauma and adverse outcomes following vacuum extraction are no more common in neonates weighing less than 2500 g than those with higher birth weights, even in failed vacuum cases.