(CNN) South Carolina Gov. Nikki Haley signed a bill into law on Wednesday that makes it illegal for a woman to obtain an abortion after her pregnancy reaches 20 weeks, press secretary Chaney Adams said.

The law takes effect immediately. Abortions may be performed after 20 weeks only if the mother's life is in jeopardy, Adams said. The bill does not provide exceptions for rape or incest.

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The Pain-Capable Unborn Child Protection Act says there is "substantial medical evidence" that fetuses can feel pain by 20 weeks.

"After twenty weeks, the unborn child reacts to stimuli that would be recognized as painful if applied to an adult human, for example, by recoiling," the bill says.

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