A while ago, Molly and I talked about “Can you get pregnant on your period?” on Stuff Mom Never Told You. And in brief, yes, you can. Sometimes, ovulation and menstruation can overlap just enough to where sperm hanging around after intercourse could possibly fertilize an egg. Oops.
But what about being on birth control, you ask? Well, according to MomStuff listener and evolutionary psychologist Diana Fleischman, the period is actually the dodgiest time of the month for women taking oral contraceptives. She writes:
One really important point from your recent podcast “can you get pregnant on your period?” that you missed –the time that you are MOST likely to get pregnant if you are on the pill is when you are on your period. The placebo pills you take that make you have a withdrawal bleed (just bleeding from the withdrawal of hormones and not really considered a proper period) do not have the hormones in them that inhibit ovulation. Some women will actually ovulate or the follicle containing an ovum will begin to develop in the pill free interval when they are bleeding.
The most dangerous time to forget or skip a pill is the first few days of the pill regimen because you are adding time for your ovaries to produce their own endogenous (from within the body) hormones on top of the pill-free interval. There has been talk of decreasing the pill free interval to make it less likely to get pregnant and I think there are some pills designed that way.
Researchers address that oral contraceptive overlap in this study.
This friendly PSA isn’t meant to scare anyone out of having sex. It’s just a friendly reminder that it’s best to be not only safe about sex, but also smart.