Int J Gynaecol Obstet. 2025 Nov 15. doi: 10.1002/ijgo.70667. Online ahead of print.
ABSTRACT
OBJECTIVE: To evaluate whether metal cup size influences maternal and neonatal morbidity in vacuum-assisted deliveries (VAD).
MATERIALS AND METHODS: Retrospective cohort at a single tertiary center (2011-2022) comparing 60-mm versus 50-mm Malmström cups. A 1:1 matched cohort analysis balanced maternal and obstetric variables. Primary neonatal outcomes were a birth trauma composite outcome (brachial plexus injury, cephalohematoma, subgaleal or subdural hematoma) and a severe neonatal composite outcome (neonatal intensive care unit admission, 5-min Apgar score less than 7, umbilical artery pH less than 7.1, intraventricular hemorrhage, hypoxic ischemic encephalopathy, or neonatal convulsions). The primary maternal composite outcome included postpartum hemorrhage, third- or fourth-degree perineal tears or need for postpartum blood products.
RESULTS: After matching, 1564 patients were included (782 per group). The 60-mm cup was associated with fewer cup detachments (22 [2.8%] versus 41 [5.2%], P = 0.015), a shorter interval to delivery (4.3 ± 1.9 versus 4.7 ± 2.4 min, P = 0.003) and a comparable failure rate leading to cesarean delivery (5 [0.6%] versus 7 [0.9%], P = 0.56). The neonatal birth trauma composite outcome was less prevalent with 60-mm cups (51 [6.5%] versus 72 [9.2%]; odds ratio [OR] 0.69, 95% confidence interval [CI] 0.47-0.99, P = 0.049) whereas the severe neonatal composite outcome did not differ (83 [10.6%] versus 96 [12.3%], P = 0.302). Maternal composite outcome was similar between groups; however, perineal tears were less common with 60-mm cups (306 [39.1%] vs 369 [47.2%]; OR 0.72, 95% CI 0.59-0.88; P = 0.001).
CONCLUSION: In VAD, use of a larger Malmström cup (60 mm) is associated with fewer cup detachments and a reduced risk of neonatal birth trauma without increasing maternal morbidity.
PMID:41239839 | DOI:10.1002/ijgo.70667
