From the Planned Parenthood website:
Quote:
How Do Birth Control Pills Work?
It's pretty common for people to be confused about how birth control pills work. Here’s what it boils down to: birth control pills are made of hormones. Hormones are chemicals made in our bodies. They control how different parts of our bodies work.
Some birth control pills contain two hormones — estrogen and progestin. These are called combination pills. Some are progestin-only pills. Most women on the pill take combination pills.
The hormones in the pill work by keeping a woman’s ovaries from releasing eggs — ovulation. Pregnancy cannot happen if there is no egg to join with sperm. The hormones in the pill also prevent pregnancy by thickening a woman’s cervical mucus. The mucus blocks sperm and keeps it from joining with an egg.
The hormones also thin the lining of the uterus. In theory, this could prevent pregnancy by keeping a fertilized egg from attaching to the uterus.
|
So that's how I always understood it. And your uterus still "sheds" but is thinner and not what it would be if you weren't on the pill.
Like I wouldn't think to think I could be pregnant if I were still getting a period. Hmm...