[Twin-to-twin delivery interval: is a time limit justified?]

To assess the effect of the twin-to-twin delivery interval on the umbilical cord blood gas status and the neonatal outcome of the second twin following vaginal delivery.

Retrospective study of twin deliveries at or beyond 34 weeks of gestation over a period of five years. The correlation between the twin-to-twin delivery interval, and the umbilical arterial blood gas parameters of the second twin, including pH, PO(2), PCO(2), HCO(3-) and base excess, was studied. A second analysis was performed after exclusion of non-vertex presentation, need for general anesthesia, growth restriction and weight difference between the twin>30%.

Two hundred and thirty-nine patients were studied. The mean twin-to-twin delivery interval was 11.3+/-6.4 minutes (between 6 and 14 minutes in 56.1% of cases). The second twin had more Apgar score<7 at 1 minute (P<0.02) and more arterial ombilical pH<7.20 (P<0.01) than the first twin. Over 15 minutes, the mean arterial pH was lower (P<0.01) and the number of arterial pH<7.20 increased (P<0.03). In contrast, the mean Apgar score and the rate of neonatal transfer did not differ significantly. There were significant negative correlations between arterial pH, base excess and bicarbonates and the twin-to-twin delivery interval (P<0.05). Similar results were found in the homogenised population. The reduction in the second twin arterial pH was expressed as pH=7.282-0.003 x time.

Umbilical cord arterial blood gas parameters deteriorate with increasing twin-to-twin delivery interval. Our results suggest that this interval should be less than 15 minutes, but obstetrician should adapt to every clinic situation.