Aug. 15, 2007 -- The abortion pill RU-486 is no riskier to future pregnancies than surgical abortion, a U.S./Denmark study shows.

French researchers reported in 2003 that women who had RU-486-induced abortions -- what doctors call "medical abortions" -- were nearly three times as likely to suffer ectopic pregnancies.

In ectopic pregnancy, the fertilized egg attaches outside the uterus, usually to the fallopian tubes. These "tubal pregnancies" do not result in live births and can affect a woman's future fertility.

To see whether RU-486 really increases the risk of ectopic pregnancy -- or other risks to future pregnancies -- U.S. National Institutes of Health researcher Jun Zhang, MD, PhD, and colleagues looked at Denmark's extensive medical database.

They compared 2,710 women who had an RU-486 abortion to 9,104 women who had a surgical abortion.

The bottom line: Women who used RU-486 had no increased risk of ectopic pregnancy, miscarriage, preterm birth, or low-birth-weight babies when they eventually decided to have a baby.

"By now, probably more than 5 million women worldwide have had RU-486 abortions," Zhang tells WebMD. "More than half of women seeking early abortion use this method. So this is a very significant finding about the safety of this treatment."

Jean Bouyer, PhD, of the French Institute of Health and Medical Research, led the earlier study linking RU-486 to ectopic pregnancy. Bouyer says the Zhang study does not prove that RU-486 is safe -- just that it is as safe as other kinds of abortion.

"Their reasoning is indirect," Bouyer told WebMD via email. "No difference was found between medical and surgical abortion. Surgical abortion is 'known' to be safe, thus medical abortion is safe, too."

But Zhang and colleagues say it is simply not accurate to directly compare women who have had abortions with women who have never had an abortion. These women differ in many respects that affect future pregnancies, including socioeconomic status, smoking status, and other health-related conditions and behaviors.

Zhang notes that the Bouyer study included only 24 women who had only medical abortions.

"When you have such a small number, you always have a possibility the finding is by chance," Zhang says.

Bouyer defends the study, which was designed not to look at the question of RU-486 safety but to find out possible risk factors for ectopic pregnancy.

"The definite interpretation of the relationship between abortion and ectopic pregnancy -- if any -- remains somewhat unclear to me," Bouyer notes.

Zhang and colleagues report their findings in the Aug. 16 issue of The New England Journal of Medicine.

SOURCES: Virk, J. The New England Journal of Medicine, Aug. 16, 2007