Todd Akin, a member of the House of Representatives and recently appointed Senate nominee for Missouri, made the claim during an interview in which he attempted to explain his no-exceptions policy in regards to abortion.
In reference to pregnancy resulting from rape, Akin told KTVI-TV: "First of all, from what I understand from doctors, that is really rare."
He continued: "If it is a legitimate rape, the female body has ways to try and shut that whole thing down."
But if that "didn't work", then the punishment should be "on the rapist and not attacking the child", Akin added.
A video clip of the interview soon went viral, leading to online criticism directed at the Republican politician.
Akin recently won the GOP nomination for a Senate seat that he is currently favourite to win.
The incumbent senator he hopes to beat, Democrat Claire McCaskill, was among those who rebuked him online as the term "legitimate rape" began trending on Twitter.
"As a woman & former prosecutor who handled 100s of rape cases, I'm stunned by Rep Akin's comments about victims this AM," she tweeted.
Medical studies in the US suggest that 5% of rapes result in the victim becoming pregnant, with around 32 000 pregnancies in the US every year being the result of rape.
In a statement, Akin later claimed that he "misspoke" and that his off-the-cuff remarks did not "reflect the deep empathy I hold for the thousands of women who are raped and abused every year".
But the fallout from the remarks may have already damaged his prospects in the Missouri race and will give encouragement to Democrats who fear losing the senate seat in the forthcoming general election.
Akin later backtracked, saying in a statement:
"In reviewing my off-the-cuff remarks, it's clear that I misspoke in this interview and it does not reflect the deep empathy I hold for the thousands of women who are raped and abused every year."
He promised that rape victims "will have no stronger advocate in the Senate to help ensure they have the justice they deserve" if he was elected.
However, Akin did not back down on his position opposing abortion in the case of rape, adding: "I believe deeply in the protection of all life, and I do not believe that harming another innocent victim is the right course of action."
Republican presidential candidate Mitt Romney's campaign distanced itself from Akin's position.
"Governor Romney and congressman [Paul] Ryan disagree with Mr. Akin's statement, and a Romney-Ryan administration would not oppose abortion in instances of rape," the statement read. – © Guardian News and Media 2012