How does it prevent pregnancy even if a couple does unprotected sex? (I’m aware it’s not 100% effective but still)
In: Biology
GYN here- the main effect of birth control pills on the market now is to thicken cervical mucous. Earlier pills in 60s-70s had a higher dose of estrogen (50 micrograms and up) which would prevent ovulation. The newer pills nowadays have way less estrogen (or none at all). The progestins (all of them) thicken cervical mucous and prevent pregnancy by keeping sperm from entering the uterus. Sometimes you won’t ovulate, but that’s not the main method of action anymore. A side effect is thinned endometrial lining which makes periods lighter
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