TLDR Version: "The pill" prevents ovulation
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Progesterone and Estradiol remain high all the time.
What does that mean?
If an egg DOES implant, the placenta produces estrogens and progesterone (as well as other things) keeping the levels of these two hormones high during pregnancy.
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That means, it doesn't shed the endometrium (no bleeding) and it doesn't release an egg (you can't grow two babies on different clocks in the same uterus for many reasons).
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"The pill" (conbination pill of estrogen and progesterone) prevents ovulation entirely by convincing your body you're already pregnant.
The "mini-pill" (just progesterone) may prevent ovulation, and makes it hard for sperm to fertilize an egg if it's there
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Hormonal IUDs work by releasing progesterone directly into the uterus in high enough dosages to prevent ovulation
Copper IUDs release copper ions that are toxic to sperm and thickens your mucous.
Neither prevent implantation.
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