Ultrasound vs routine care before instrumental vaginal delivery: A systematic review and meta-analysis

The objective was to report the role of intrapartum ultrasound examination in affecting maternal and perinatal outcome in women undergoing instrumental vaginal delivery.

MEDLINE, Embase, CINAHL, Google Scholar and ClinicalTrial.gov databases were searched. Inclusion criteria were randomized controlled trials comparing ultrasound assessment of fetal head position vs routine standard care (digital examination) before instrumental vaginal delivery (either vacuum or forceps). The primary outcome was failed instrumental delivery extraction followed by cesarean section. Secondary outcomes were postpartum hemorrhage, 3rd or 4th degree perineal lacerations, episiotomy, prolonged hospital stay, Apgar score<7 at 5 min, umbilical artery pH <7.0 and base excess greater than -12 mEq, admission to neonatal intensive care unit (NICU), shoulder dystocia, birth trauma, a composite score of adverse maternal and neonatal outcome and incorrect diagnosis of fetal head position. Risk of bias was assessed using the Revised Cochrane risk-of-bias tool for randomized trials (RoB-2). The quality of evidence and strength of recommendations were assessed using the Grading of Recommendations Assessment Development and Evaluation (GRADE) methodology. Head-to-head meta-analyses using a random-effect model were used to analyze the data and results are reported as relative risk with their 95% confidence intervals.

Five studies were included (1463 women). There was no difference in the maternal, pregnancy or labor characteristics between the two groups. An ultrasound assessment prior to instrumental vaginal delivery did not affect the cesarean section rate compared with standard care (p = 0.805). Likewise, the risk of composite adverse maternal outcome (p = 0.428), perineal lacerations (p = 0.800), postpartum hemorrhage (p = 0.303), shoulder dystocia (p = 0.862) and prolonged stay in hospital (p = 0.059) were not different between the two groups. Composite adverse neonatal outcome was not different between the women undergoing and those not undergoing ultrasound assessment prior to instrumental delivery (p = 0.400). Likewise, there was no increased risk with abnormal Apgar score (p = 0.882), umbilical artery pH < 7.2 (p = 0.713), base excess greater than -12 (p = 0.742), admission to NICU (p = 0.879) or birth trauma (p = 0.968). The risk of having an incorrect diagnosis of fetal head position was lower when ultrasound was performed before instrumental delivery, with a relative risk of 0.16 (95% confidence interval 0.1-0.3; I² :77%, p < 0.001).

Although ultrasound examination was associated with a lower rate of incorrect diagnoses of fetal head position and station, this did not translate to any improvement of maternal or neonatal outcomes.