By Mary Wisniewski

CHICAGO (Reuters) - Democrat Tammy Duckworth, a decorated Iraq War veteran who headed President Barack Obama's Department of Veteran Affairs, beat incumbent Republican Joe Walsh for an Illinois congressional seat on Tuesday.

Walsh stirred controversy last month with a suggestion that abortion is never necessary to save the life of a mother. Walsh was one of three Republican congressional candidates this election season whose chances were harmed by controversial remarks about abortion.

Backed by the Tea Party movement, Walsh was elected in 2010 by just 292 votes and joined a class of first-term Republicans whose resistance to compromise was a hallmark of a dysfunctional Congress.

Although Republicans will retain the majority in the U.S. House of Representatives, Democrats made gains in Illinois, also defeating incumbent Republican, Judy Biggert, in another Chicago suburban district.

Democrat Bill Foster defeated Biggert in a district that was redrawn to favor Democrats after the 2010 census. A third hotly contested suburban race, between Democrat Brad Schneider and incumbent Republican Robert Dold, was too close to call.

In Illinois, Democrats began the election year determined to reverse a Republican gain of four U.S. House seats in 2010. The powerful Illinois state house speaker, Michael Madigan, used Democratic power in state government to redraw election districts in a way that would help Democratic candidates.

Duckworth, who was featured at the Democratic National Convention, opened up a double-digit lead after Walsh said on October 18 that abortion was never necessary to save a woman's life. The congressman later softened his remarks, which were criticized by medical experts, to say such instances were "extremely rare."

Walsh's remarks came two months after a statement by Missouri Republican Senate candidate Todd Akin that women have biological defenses against pregnancy in the case of "legitimate rape." Also, Indiana Republican Senate candidate Richard Mourdock said October 23 that a pregnancy resulting from rape was "something God intended to happen." Both Akin and Mourdock lost Tuesday to Democrats.

Duckworth, 44, who lost both legs and part of her right arm in Iraq, had previously run unsuccessfully for Congress in 2010.

(Reporting By Mary Wisniewski and Samuel P. Jacobs; Editing by Greg McCune, Bernard Orr)