What Happens to Your Period if You Get Pregnant? 

By Kenley Dotson, Period Pro from University of Louisville School of Medicine

Kenley Dotson, Period Pro

What happens to your period if you get pregnant?

The short answer: it stops. 

But why?

Most people describe their period as the bleeding and physical symptoms, like cramping, that happen when the uterine lining sheds because an ovulated egg is not fertilized. A period is just one phase of the entire menstrual cycle, which is much more complicated than just the monthly bleeding people think of as their period. There are four phases that make up the menstrual cycle: menstrual phase, follicular phase, ovulation, and the luteal phase. All four phases of the menstrual cycle occur when the egg is NOT fertilized afterring ovulation. 

However, if the egg IS fertilized and continues to grow, it attaches to the uterine lining and the hormone progesterone is required to keep it growing. The name progesterone literally means “pro-gestation,” and “gestation” is another word for pregnancy; so progesterone is the hormone that supports pregnancy, or allows it to grow. When someone is pregnant, progesterone continues to be released which signals that the uterus should NOT shed its lining because that lining is needed for the pregnancy to grow. When there is NO pregnancy, progesterone levels drop rapidly, and that signals that the uterine lining needs to be released, so it can rebuild itself for the next cycle.  

Although periods don’t happen in pregnancy, pregnant people may still experience some vaginal bleeding. A small amount of spotting or bleeding can occur when the embryo implants in the uterine lining (the endometrium), and is called implantation bleeding. Any  moderate to heavy bleeding accompanied by cramping or pain, should prompt medical attention because it could be a sign of a miscarriage or an ectopic pregnancy (a medical emergency that happens when a pregnancy grows outside of the uterus, usually in a fallopian tube).

Many people who experience bleeding during pregnancy have normal pregnancies and healthy babies, but it is always very important to get prompt medical attention for any bleeding in pregnancy.