Women who are given drugs to induce labor are nearly twice as likely to suffer an amniotic fluid embolism, a rare but potentially fatal complication of pregnancy, according to a study published on Friday.

Researchers for the Maternal Health Study Group of the Canadian Perinatal Surveillance System studied more than three million deliveries of babies in Canada over a 12-year period.

In 185 cases, women experienced the rare complication in which the amniotic fluid that surrounds a baby in the womb enters the bloodstream and causes a blockage, they wrote in the Lancet medical journal.

In 24 of those cases, the mothers died.

The women had been given drugs to induce labor in just 17 percent of the deliveries. But those accounted for 52 of the amniotic fluid embolisms - 28 percent - and 10 of the fatal cases, or 42 percent.

“We should emphasize that the absolute risk of increase of amniotic fluid embolism for women undergoing medical induction of labor is very small: four or five total cases and one or two fatal cases per 100,000 women induced,” the authors wrote.

“However, with 4 million births per year and induction rates approaching 20 percent in the USA, this practice could be causing amniotic fluid embolism in 30-40 women per year in the USA alone, including 10-15 deaths,” they wrote.

“Although the small absolute risk of amniotic fluid embolism is unlikely to affect the decision to induce labor in the presence of compelling clinical indications, women and physicians should be aware of the risk if the decision is elective.”