Temporary disruption of the menstrual cycle is commonly experienced after the use of the morning-after pill. If taken before ovulation, the high doses of progestogen in levonorgestrel treatments may induce progestogen withdrawal bleeding a few days after the pills are taken. If levonorgestrel is taken after ovulation, it may increase the length of the luteal phase, thus delaying menstruation by a few days. If a woman's menstrual period is delayed by a week or more, it is advised that she take a pregnancy test.
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