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How does an ultrasound date you off your lmp if you dnt remember it and why do i hear the exact weeks and days they give you on a ultrasound arent when you conceived it when your lmp was....

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Asked by Anonymous at 6:54 AM on May. 3, 2011 in Pregnancy

Answers (2)
  • Ok... if you go by your LMP the date can vary because who knows when *exactly* in your cycle you conceived? They make an educated guess. Some women conceive during their period, you just never know.
    With an ultrasound they go by how far the fetus has developed at that point. But again, it can possibly be off, but probably more like a few days rather than a few weeks.
    Now, with an ultrasound you are pretty close to figuring out when you conceived but you mist remember that sperm can live in your body anywhere from 3-7 days. The moment you conceive is when the sperm and egg meet, but it could have been sperm from sex 4 days before that. Get it?
    FYI that is how it is possible to give birth to non-identical (fraternal? Can't remember the right word lol) twins by 2 different fathers. A little off topic, but an interesting tidbit, I think lol

    Answer by Nicoles2LilRams at 7:37 AM on May. 3, 2011

  • Yeah...they use your "maybe" LMP and work some math equation with the length of baby's bones and deduce to a estimated date.

    Answer by BradenIsMySon at 8:24 AM on May. 3, 2011

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