CHICAGO (Reuters) - A Republican congressman from Illinois waded into controversy with a suggestion that abortion is never necessary to save the life of a mother, two months after a colleague drew fire for saying women were unlikely to become pregnant from "legitimate rape."

Representative Joe Walsh, who opposes abortion, made the remarks to reporters on Thursday after a debate with Democratic challenger Tammy Duckworth, his opponent for a House seat representing the Chicago suburbs.

"There is no such exception as life of the mother. And as far as health of the mother, same thing, with advances in science or technology, health of the mother had been, has become a tool for abortions anytime under any reason," Walsh told reporters Thursday.

With the U.S. presidential election less than three weeks away, abortion is a key issue that divides Democrats and Republicans. The Republican Party platform opposes abortion even in cases of rape and incest, while the Democratic platform supports a woman's right to a "safe and legal" abortion.

In a statement Friday, Walsh clarified his remarks, saying abortion is not necessary outside of "very rare exceptions" such as ectopic pregnancies and other rare health issues.

Walsh said that outside those circumstances, "the research is pretty clear that with the advances in modern medicine, an invasive and traumatic procedure like an abortion is not necessary to save the life of a mother."

The American Congress of Obstetricians and Gynecologists, which has 56,000 members, said abortions were necessary "in a number of circumstances to save the life of a woman or to preserve her health."

"Unfortunately, pregnancy is not a risk-free life event, particularly for many women with chronic medical conditions," the group said in a statement, noting that more than 600 women die in the United States each year from pregnancy and childbirth-related causes.

Though Walsh called them "very rare," the Centers for Disease Control and Prevention reports that ectopic pregnancies occur in 1 percent to 2 percent of U.S. pregnancies, and account for 3 percent to 4 percent of pregnancy-related deaths. Ectopic pregnancy involves the fertilized ovum implanting on any tissue other than the endometrial lining of the uterus.

The Chicago Tribune reported that Walsh said on Thursday that medical advances had made it unnecessary to ever perform an abortion to save a mother's life.

"With modern technology and science, you can't find one instance," the paper quoted him as saying.

The controversy over Walsh's remarks echoes a storm over comments by Missouri Republican senatorial candidate Todd Akin in August. He said that women have biological defenses against pregnancy in the case of "legitimate rape."

Akin was criticized and asked to withdraw from the Senate race by members of his own party. He later apologized for the remark.

Duckworth's campaign said in a statement she was saddened by Walsh's remarks.

"Prohibiting a woman to have an abortion when her life is at risk shows a blatant disregard for the facts and a carelessness which is not acceptable from an elected official," she said.

Dr. Anne Davis, a gynecologist at Columbia University Medical Center in New York City and consulting medical director for Physicians for Reproductive Choice and Health, said sometimes it was necessary to end a pregnancy to save the life of a mother.

She said abortions could be necessary as a result of chronic health conditions, like a heart problem, or because of problems during pregnancy such as infections or excessive bleeding.

"This isn't once in a blue moon. This happens all the time," Davis said, noting one or two such emergency procedures must be performed each year at her hospital alone. "I wish it never happens. But that is not the truth."

(Reporting by Mary Wisniewski; Editing by Cynthia Johnston and Jim Loney)