By Dr. Roshini Raj

As you know, your body changes drastically with each pregnancy, but it doesn’t stop at an expanding belly. For example, you produce about 100 times as much estrogen during a day of pregnancy as on a normal day. Other hormones, like progesterone and human chorionic gonadotropin, increase during this time as well. These temporary hormonal shifts alter your body not only during those nine months—they can have lasting effects, even after you’re done giving birth and have finished nursing.

This means that just as your breasts may never look quite the same again, your periods may become unrecognizable. Some women experience a pattern shift (differences in PMS symptoms, cramps, duration or heaviness, mood changes or all of the above) after their first baby, and then may go through another menstrual 180 after their second or third child. Still others have no changes at all.

Your period pattern may also undergo an adjustment in your late 30s as estrogen and fertility begin to decline. So your monthly deluge could be due to a combination of factors. If heavier bleeding or increased pain is making your periods harder to cope with, see your doctor; birth control pills can help even out your hormones.

Health’s medical editor, Roshini Rajapaksa, MD, is assistant professor of medicine at the NYU School of Medicine.

Originally published on Health.com