Sildenafil does not improve perinatal outcomes related to hypoxia during labour

Treatment with sildenafil citrate during labour falls short of reducing the incidence of adverse perinatal outcomes potentially related to intrapartum hypoxia, according to a study.

The study was conducted at 13 Australian hospitals and included 3,257 women with singleton or dichorionic twin pregnancies and planning vaginal birth at term via either spontaneous labour or induction of labour. These women were randomly assigned to receive 50 mg oral sildenafil citrate every 8 hours up to 150 mg (1,626 women, 1,634 infants) or equivalent placebo (1,631 women, 1,641 infants).

The efficacy of sildenafil vs placebo was examined in terms of the primary composite outcome of intrapartum stillbirth, neonatal death, Apgar score <4 at 5 minutes (indicative of severe neonatal depression at birth), acidosis at birth (umbilical cord artery pH <7.0), hypoxic ischemic encephalopathy, neonatal seizures, neonatal respiratory support for greater than 4 hours, neonatal unit admission for greater than 48 hours, persistent pulmonary hypertension of the newborn, or meconium aspiration syndrome. The individual components of the primary composite and emergency caesarean delivery or instrumental birth for intrapartum foetal distress were also assessed as secondary outcomes.

In the sildenafil and placebo groups, mean maternal age (31.7 vs 31.5 years) and gestation at randomization (39.5 vs 39.5 weeks) were similar. More than half of the women in the two groups were of Australia/New Zealand ethnicity (19.4 percent vs 19.1 percent) and were nulliparous (58.1 percent vs 59.3 percent). Labour was induced for 83.5 percent of women in the sildenafil group and in 82.9 percent in the placebo group.

The primary outcome occurred in 5.1 percent of women in the sildenafil group and in 5.2 percent in the placebo group, with the difference not statistically significant (relative risk, 1.02, 95 percent confidence interval [CI], 0.75–1.37).

Compared with placebo, sildenafil citrate had no significant effect on emergency caesarean delivery or instrumental vaginal birth for foetal distress (relative risk, 1.12, 95 percent CI, 0.98–1.29) or on any of the individual components of the primary outcome.

Treatment effects were consistent across all subgroups.