Head position and vacuum-assisted delivery using the Kiwi Omnicup

To evaluate the association between fetal head position during prevacuum assessment and adverse outcomes.

This retrospective cohort study included all vacuum-assisted deliveries using the Kiwi Omnicup over 5 years. Primary outcomes were third- or fourth-degree perineal tear, pH < 7.1, and subgaleal hematoma (SGH). AGAR, neonatal intensive care unit admission, cephalohematoma, Erb's palsy, third-stage duration, and postpartum hemorrhage were secondary. Outcomes were compared between the occiput posterior (OP) and occiput anterior (OA) positions.

The study included 1960 patients. OP position was more likely to involve epidural analgesia (311 [82.5%] vs. 1216 [77%], P = 0.020), higher fetal head station (P = 0.001), higher percentage of cup detachments (121 cases [32.1%] vs. 307 [19.4%], P = 0.001), and longer procedure (5.5 ± 3.7 min vs. 4.7 ± 2.8 min, P = 0.001). OP was associated with umbilical cord pH < 7.1 (21 [5.5%] vs. 52 [3.9%], P = 0.032), NICU admissions (16 [4.2%] vs. 38 [2.4%], P = 0.049), SGH (18 [4.8%] vs. 38 [2.4%], P = 0.013), and high-degree perineal tears (12 [3.2%] vs. 26 [1.7%], with borderline significance, P = 0.051). SGH and high-grade tears remained significantly associated with OP position (P = 0.008 and P = 0.016, respectively) after adjusting for maternal age, nulliparity, diabetes, epidural anesthesia, preprocedure head station, and birth weight.

OP position is an independent risk-factor for anal sphincter injury and SGH during vacuum-assisted delivery.