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

WSJ: Judge Eases Restrictions on Plan B Emergency Contraceptive

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.

WSJ: Judge Eases Restrictions on Plan B Emergency Contraceptive

If there has been fertilization, Plan B may prevent a fertilized egg from embedding in the uterus.

CNN: SHARE THIS

The Plan B emergency contraceptive pill works by preventing ovulation or by blocking a potentially fertilized egg from becoming implanted in a woman's uterus, according to the drug's label.

WSJ: Corrections & Amplifications