Understanding Ultrasounds and Early Pregnancy – What to Expect

Question
QUESTION: Thanks so much for answerin my question i just didnt know if a ultrasound would count implantation bleeding as lmp? and why does an ultrasound measure you by lmp if you dont remember it? and what are the fist 2weeks of pregnancy?

ANSWER: Dear Michelle,
An ultrasound doesn't actually detect the menstrual bleeding. What it does is measure the baby's size, and figure out how much the baby has developed (does it have lungs yet? kidneys? intestines? etc.). Based on those two things, they could figure out how many weeks you've been pregnant. So now they know when you conceived (give or take a few days, but the very early ultrasounds are pretty accurate). Then they count two weeks back from the date they figure you probably conceived, and call that your LMP. So the first two weeks of pregnancy (how they count it) you weren't really pregnant. When they say 40 weeks of pregnancy, they count from your LMP, so you are really only pregnant for 38 weeks.
Good luck, and feel free to ask anything else!
Sheva

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QUESTION: So if it says i was 13wks and 5days on the ultrasound screen that means i really conceived 11wks and 5days ago? and so how do i figure out if the period i had was a period and  not implantation bleeding? my due dates are july 31 and another one is aug 5th idk which one to go off the due date of july 31 i didnt tell them my lmp and the other doc i told them my period was oct 30 and that gave me the aug 5th due date i just need to make sure there no possible way i got pregnant in october

Answer
You have to ask your doctor to be absolutely sure of what the dates on the screen mean. Usually it means 13 weeks, 5 days from your LMP, and 11 weeks, 5 days from conception, like you said, but just to be on the safe side, I would ask to be sure.
Based on the dates you gave me, it sounds like you conceived in early to mid-November.

It doesn't sound like you could have conceived in October, but if there is a question of paternity, I always suggest testing to be sure.
Best of luck,
Sheva