Randomised Italian Sonography for Occiput POSition Trial Ante Vacuum (R.I.S.POS.T.A.)

OBJECTIVE: To assess whether the ultrasound diagnosis of fetal head position reduces the risk of failed vacuum delivery and improves labor outcomes. METHODS: R.I.S.POS.T.A. (Randomised Italian Sonography for Occiput POSition Trial Ante Vacuum) was a randomised controlled trial conducted from April 2014 to June 2017 and involving thirteen Italian maternity hospitals. Singleton term pregnancies with cephalic presentation where a decision for instrumental delivery by vacuum extractor was made were included. Patients were randomized to either vaginal examination (VE) only (Group A) or VE plus transabdominal ultrasound (US) evaluation (Group B) to determine fetal head position before attempted instrumental delivery. The primary outcome of the study was the emergency Caesarean section rate due to failed vacuum delivery. A sample size of 653 per group (n=1306) was planned to compare the primary outcome between the two groups. The sample size estimation was based on the hypothesis that the risk of failed vacuum delivery in the VE group would be 5% and that ultrasound assessment of fetal position prior to vacuum would decrease this risk to 2%. RESULTS: Overall, 222 women were randomized and 221 were included in data analysis, of whom 132 (59.4%) were randomized to VE and 89 (40.6%) to VE plus US evaluation prior to vacuum delivery. No significant differences in the occurrence of emergency Caesarean section due to failed instrumental delivery and in other maternal and fetal outcomes were noted between the two groups. At interim analysis (n=221), the trial was stopped for futility. Women randomized to VE plus US showed higher rates of episiotomy and non-occiput anterior (OA) position at randomization and at delivery, and a lower incidence in incorrect diagnosis of non-OA position. CONCLUSIONS: Our prematurely stopped randomised trial did not demonstrate any reduction in failed instrumental delivery and maternal and fetal morbidity in women submitted to sonographic assessment of fetal position prior to vacuum delivery. This article is protected by copyright. All rights reserved.