Eli5: Why is pregnancy counted from the first day of your last period?
In: Biology
Your last period started a new cycle, you released an egg, it got fertilized with a man’s sperm and now you’re pregnant.
Ovulation usually happens 2ish weeks after your period, but that’s not a hard guarantee by any means even if your cycle is pretty regular.
Since you don’t know exactly when you ovulated, the count starts from your last period for simplicity’s sake.
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