ROME, Oct. 11  A comprehensive global study of abortion has concluded that abortion rates are similar in countries where it is legal and those where it is not, suggesting that outlawing the procedure does little to deter women seeking it.

Moreover, the researchers found that abortion was safe in countries where it was legal, but dangerous in countries where it was outlawed and performed clandestinely. Globally, abortion accounts for 13 percent of women’s deaths during pregnancy and childbirth, and there are 31 abortions for every 100 live births, the study said.

The results of the study, a collaboration between scientists from the World Health Organization in Geneva and the Guttmacher Institute in New York, a reproductive rights group, are being published Friday in the journal Lancet.

“We now have a global picture of induced abortion in the world, covering both countries where it is legal and countries where laws are very restrictive,” Dr. Paul Van Look, director of the W.H.O. Department of Reproductive Health and Research, said in a telephone interview. “What we see is that the law does not influence a woman’s decision to have an abortion. If there’s an unplanned pregnancy, it does not matter if the law is restrictive or liberal.”