| Re: how is it possible to have a negative blood pregnancy test but actually be pregna
The blood test looks for something called HGH, a hormone that the fetus produces. However, for the first 7-10 days after intercourse, the fetus is not yet attached to the wall of your uterus, so it can't affect your blood. For the first few weeks of development, the fetus is so small you could barely see it, so the amount of hormone it produces is also tiny.
It's unlikely you would test positive less than 14 days after the sex in question, and sometimes it takes a month or more.
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