To reduce the risk of illness and death, twins should be delivered before 40 weeks of gestation, but there is no added benefit in delivering them by 38 weeks of gestation, new research suggests. In fact, delivery at 37 weeks appears to raise the risk of needing assisted ventilation.

The findings run counter to some reports that have suggested improved outcomes with delivery by 38 weeks gestation. Still, other studies, like the current one, have failed to identify a benefit with earlier delivery.

The latest findings, which appear in the American Journal of Obstetrics and Gynecology, are based on a look at 60,443 twin pairs that were delivered in the US between 1995 and 1997. The study only included pregnancies that had reached at least 37 weeks of gestation.

Compared with twins delivered at 37 weeks gestation, those delivered at or beyond 40 weeks were over 2.5-times more likely to die.

By contrast, delivery at 38 and 39 weeks gestation did not significantly increase or decrease mortality relative to delivery at 37 weeks.

Similarly, delivery at or beyond 40 weeks gestation increased the risk of low Apgar scores by at least 74 percent, lead author Dr. Jennifer E. Soucie, from the University of Ottawa in Ontario, Canada, and colleagues note. Apgar scoring is a method of quickly checking newborns, based on their heart rate, breathing, muscle tone, response to stimulus and color.

Delivery at 39 weeks cut the likelihood of ventilation use by 17 percent relative to delivery at 37 weeks, the report indicates.

“This study suggests that the optimal date of delivery for twins should be <40 weeks of gestation, and we did not identify compelling evidence (such as, decreased risk of morbidity) for being delivered at <38 weeks of gestation,” the investigators conclude.

SOURCE: American Journal of Obstetrics and Gynecology July 2006.