The synthetic hormones in the pill prevent pregnancy by thinning out the lining of the uterus, stopping ovulation and preventing fertilization. The lining of the uterus (also called the endometrium) is what sheds during menstruation. Birth control is pretty powerful, so sometimes it can thin out your endometrium so much that there’s nothing to shed during your period. This is why it’s common for many women to not get their period on birth control, even during their placebo pill week.
Menstruation is triggered by a drop in the hormones estrogen and progesterone, both of which are artificially produced by the pill. This means that menstruating on the pill isn’t a real period so much as it is “withdrawal bleeding” produced by a lack of artificial hormones. Your period is not a medically necessary process. It’s just your body’s way of telling you that you’re not pregnant. This is why it’s totally safe to use birth control to skip your period entirely, either by using extended-use birth control pills that allow for four periods a year, or by skipping the placebo week of your 21 or 28 day pack. It’s also normal to experience breakthrough bleeding outside of your placebo week—in fact, 1 in 5 women will experience this when starting a new pill. That being said, this breakthrough bleeding should stop after 3 months of pill use. If it continues, contact your doctor.
If you’re on birth control and not getting your period during your placebo week, there’s no need to worry, especially if you know you’ve been taking your pill every day. It’s normal for your period to be lighter and shorter than usual, especially if you’ve been on birth control for awhile. About 10-20% of people experience very light or no period after their sixth pill pack, while 10% of people do not experience any withdrawal bleed. Take a pregnancy test if you’ve missed your period and are experiencing symptoms of pregnancy, such as morning sickness or breast soreness.
If you’re on the progestin-only minipill, know that only 50% of minipill users experience regular menstruation, so expect the unexpected when it comes to your period.
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