The history of misoprostol use for induction of labor in full-term pregnancies has been complicated by the fact that the drug is also used for termination of first-trimester pregnancies, routinely used in combination with RU-486, the so-called 'morning after' abortion pill.

Alfirevic said that despite the safety, legal and political issues surrounding misoprostol, 'Clinicians felt that they had a duty to investigate this drug because this is the only prostaglandin that could be used effectively orally. It could potentially be a lifesaving drug in developing countries, where they didn’t have access to any safe drug for abortion, induction of labor, or prevention of post-partum hemorrhage.'

Nigeria this month became the latest country to approve its use to induce labor, a procedure recommended when carrying a pregnancy is riskier than giving birth.

The updated review included 41 randomized trials – 28 of them new since the previous study – and involved 8,606 women. The studies compared misoprostol administered orally versus vaginally and compared oral misoprostol with vaginal use of the prostaglandin dinoprostone and with intravenous oxytocin. The review concluded that oral misoprostol 'appears to be at least as effective as current methods of induction.'

Although the authors found no evidence of serious problems among the participants, Alfirevic warned that 'much more data are needed before we can be confident that there are really no adverse fetal effects that can be attributed to misoprostol.' To address the risks of rare adverse outcomes, studies would need to include in excess of 30,000 women, the authors said.

Use of oral misoprostol by American obstetricians is likely to remain relatively stable for the foreseeable future, predicts Dr. Deborah Wing, a specialist in maternal fetal medicine at the University of California, Irvine. 'Because of the highly litigious nature of medical practice in the United States, there are practitioners that have grave concern about the use of the medication without FDA labeling.'

Still, Wing envisions a day when, in appropriate circumstances, a safe and effective regimen of oral misoprostol can be prescribed on an outpatient basis around a woman’s due date. 'What woman wouldn’t want to be able to take a pill to control when she went into labor?' she asks. 'But we’re a long way away from that.'

The review itself noted that 'most studies … did not assess women’s views or satisfaction rates' regarding induced labor versus possible safety risks.