Kiwi OmniCup Handheld vs. Mityvac M-Style Conventional Vacuum System: A Retrospective Observational Study

To improve choice of vacuum-assisted delivery (VAD) system, we compared outcomes of Kiwi handheld system and Mityvac M-style conventional system (both use disposable plastic cups).

Retrospective observational study with data collection from electronic medical records. The study was conducted at a tertiary medical center, with approximately 7000 deliveries annually. Categorical and continuous variables were analyzed using chi-square test and t-test, respectively. p value < 0.05 considered significant. The main outcomes assessed were the overall failure rate of each system, failure rates for occipito-anterior (OA) vs. occipito-transverse/occipito-anterior (OT/OP) positions, +1 vs. +2 fetal stations, and early maternal/neonatal outcomes.

During a 10-month period, there were 507 (8.4%) attempted VADs, 36 failed (7.1%) and 8 (1.5%) converted to cesarean section. Of these, 364 were Kiwi-assisted and 143 Mityvac-assisted. Background characteristics were similar. The handheld system had more failures overall (9.6 vs. 0.7%), at OA (7.6 vs. 0.9%) and non-OA positions (17.3% vs. none), at + 1 (13.25 vs. 0.96%) and at + 2/3 stations (6.1% vs. none), than the conventional system did, respectively. There was a higher rate of early post-partum hemorrhage (15.3 vs. 7.4%) in the conventional group. Both systems had similar rates of third/fourth degree perineal tears, shoulder dystocia and adverse neonatal outcomes.

Our results suggest more failures with Kiwi compared to Mityvac, overall and at any fetal position/station, without a significant difference in adverse outcome profile.