Short-term outcome of the second twin during vaginal delivery is dependent on delivery time interval but not chorionicity

AbstractThe decrease in pH in monochorionic (MC) second twin may exceed that of dichorionic (DC) second twin during vaginal twin delivery. The aim of this study was to investigate the effect of chorionicity on the umbilical artery pH of the second twin in relation to increased twin-to-twin delivery time interval (DTI) from 30 weeks of gestation. A hospital based cohort of all twin deliveries after 30 completed weeks of gestation with the first twin delivered vaginally between 2007 and 2012 in four delivery units in Stockholm county was conducted. The changes of umbilical pH in MC twins compared to DC twins in relation to twin-to-twin DTI was studied using linear regression. The predictors for acidosis (pH ≤ 7.10) in the second twin were studied by logistic regression. The cohort included 681 DC and 186 MC twin pairs. There was a correlation between the umbilical pH and the twin-to-twin DTI but independent of the chorionicity, the pH decreased in average by 0.0012 units/min (p < .001). Twin-to twin DTI was...