You're six weeks pregnant. That means six weeks ago an egg and a sperm met, did the happy dance together, and got the baby ball rolling in your uterus, right?

Wrong.

Pregnancy weeks are measured in a strange way, but it appears to be the most consistent method of measurement considering the varied reality of menstruation. (A 28-day cycle between periods is common, but many women have longer or shorter cycles, and some have totally irregular ones.)

A Twitter thread from NBC News's Ginger Gibson explains that pregnancy is measured from the first day of a woman's last period, which is generally approximately two weeks before an egg would ever get a chance to meet a sperm.

So technically speaking, in the first couple of weeks of pregnancy, there is no actual pregnancy. Weird, right? But that's how the "XX weeks pregnant" calculation works.

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