Vacuum-Assisted Delivery Complication Rates Based on Ultrasound-Estimated Fetal Weight

This retrospective cohort study investigated the association between ultrasonographic estimated fetal weight (EFW) and adverse maternal and neonatal outcomes after vacuum-assisted delivery (VAD). It included women with singleton pregnancies at 34-41 weeks gestation, who underwent ultrasonographic pre-labor EFW and VAD in an academic institution, over 6 years. Adverse neonatal and maternal outcomes included shoulder dystocia, clavicular fracture, or third- and fourth-degree perineal tears. A receiver-operator characteristic curve was used to identify the optimal weight cut-off value to predict adverse outcomes. Fetuses above and below this point were compared. Multivariate analysis was used to control for factors that could lead to adverse outcomes. Eight-hundred and fifty women met the inclusion criteria and had sonographic EFW within two-weeks before delivery. Receiver-operator characteristic curve analysis found that ultrasonographic EFW 3666 g is the optimal threshold for adverse outcomes. Based on these results, outcomes were compared using EFW 3700 g. The average EFW in the >= 3700 g group (n = 220, 25.9%) was 3898 +/- 154 g (average birthweight 3710 +/- 324 g). In the group <3700 g (n = 630, 74.1%), average EFW was 3064 +/- 411 g (birthweight 3120 +/- 464 g). Shoulder dystocia and clavicular fractures were more frequent in the higher EFW group (6.4% and 2.3% vs. 1.6% and 0.5%, respectively; p < 0.05). Women in the >= 3700 g group experienced more third- and fourth-degree perineal tears (3.2% vs. 1%, p = 0.02). Multivariate logistic regression analysis found maternal age, diabetes and sonographic EFW >= 3700 g as independent risk-factors for adverse outcomes. Sonographic EFW >= 3700 g is an independent risk-factor for adverse outcomes in VAD. This should be considered when choosing the optimal mode of delivery.

Automated summary

This retrospective cohort study found an association between ultrasonographic estimated fetal weight (EFW) and adverse maternal and neonatal outcomes after vacuum-assisted delivery (VAD). Fetuses with higher EFW were more likely to experience shoulder dystocia, clavicular fractures, and third- and fourth-degree perineal tears during delivery. Maternal age, diabetes, and EFW >= 3700 g were identified as independent risk factors for adverse outcomes.