Oral birth control pills contain hormones that prevent ovulation and reduce the severity of menstrual cramps.

口服含激素的药片会阻止排卵和降低痛经的严重度。

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The drug works by using high doses of the female hormone progestin, which also is contained in birth-control pills, to prevent ovulation or block a potentially fertilized egg from becoming implanted in a woman's uterus, according to the drug's label.

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