How does The Pill prevent pregnancy?

It prevents ovulation, an IUD prevents implantation. IUD’s also prevent pregnancy by giving you pelvic inflammatory disease.

They work in several ways. They prevent ovulation. They thicken cervical mucus (which blocks sperm). They also thin the lining of the uterus.

From what I understand, it depends on the kind of pill you’re using. Some do as @faye said and some thicken the mucus lining around the cervix which would prevent sperm from entering the uterus. The morning after pill actually prevents implantation.

Generally, the pill can fool your body into thinking it’s in the earliest stages of pregnancy.

@KatawaGrey So then do you know if all The Pills also prevent a zygote from attaching to the uterine wall, or is the Norgestimate & Ethinyl Estradiol combo the only one that does that?

@papayalily Depends on what they are doing to prevent them from attaching to the uterine wall. Technically by thinning the lining of the uterus, that would make it difficult for implantation. From what I read about Norgestimate & Ethinyl Estradiol, that is what it does as well. So most of the pills do that same thing.

@Seaofclouds So N&EE isn’t special, it’s just that those particular brands promote it more?

@papayalily I guess. I’ve never heard them promote that, but I don’t really listen to most of the ads for them or any other BCP.

My understanding is that scientists are not in agreement about whether any formulation of the pill prevents implantation, nor the extent to which any particular formulation does so.

The biggest thing it does is stop ovulation., This is why the pill is also used for people who get ovarian cysts, to shut down the ovaries so to speak. The other things mentioned by @Seaofclouds have been claimed as well, depending on the pill, but if you don’t ovulate that is the biggest trick in not getting pregnant while taking the pill, and that is why it prevents pregnancy so well statistically. If you don’t take it the same time every day you allow a fluctuation in the hormone, or if you don’t get enough of it because another medication interferes with it, you can accidently ovulate.