Background: Midpelvic vacuum extractions are controversial due to reports of increased risk of maternal and perinatal morbidity and high failure rates. Prospective studies of attempted midpelvic vacuum outcomes are scarce. Our main aims were to assess frequency, failure rates, labor characteristics, maternal and neonatal complications of attempted midpelvic vacuum deliveries, and to compare labor characteristics and complications between successful and failed midpelvic vacuum deliveries.
Study design: Clinical data were obtained prospectively from all attempted vacuum deliveries (n = 891) over a one-year period with a total of 6903 births (overall cesarean section rate 18.2% (n = 1258). Student's t-test, Mann-Whitney U-test or Chi-square test for group differences were used as appropriate. Odds ratios and 95% confidence intervals are given as indicated. The uni- and multivariable analysis were conducted both as a complete case analysis and with a multiple imputation approach. A p-value of <0.05 was considered statistically significant.
Results: Attempted vacuum extractions from midpelvic station constituted 36.7% (n = 319) of all attempted vacuum extractions (12.9% (n = 891) of all births). Of these 319 midpelvic vacuum extractions, 11.3% (n = 36) failed and final delivery mode was cesarean section in 86.1% (n = 31) and forceps in the remaining 13.9% (n = 5). Successful completion of midpelvic vacuum by 3 pulls or fewer was achieved in 67.1%. There were 3.9% third-degree and no fourth-degree perineal tears. Cup detachments were associated with a significantly increased failure rate (adjusted OR 6.13, 95% CI 2.41-15.56, p< 0.001).
Conclusion: In our study, attempted midpelvic vacuum deliveries had relatively low failure rate, the majority was successfully completed within three pulls and they proved safe to perform as reflected by a low rate of third-degree perineal tears. We provide data for nuanced counseling of women on vacuum extraction as a second stage delivery option in comparable obstetric management settings with relatively high vacuum delivery rates and low cesarean section rates.