Why Do The Doctors Go By Your Last Period

6 Replies
sm - October 14

I went in for my 20 week u/s and the dates matched perfect, they said I concieved around june 1st. I jst dont understand why everything is off of your last period!! It drives me nuts. If i got preg a few adys before my last period would it had changed the dates on my u/s?? Just wondering..I'm confused!! any help would be great..thanks


to sm - October 14

They go by your last period because you more than likely got pregnant after your last period. Most women ovulate 10-14 days after menstruating so you would miss your next period. Going by your last period is the most accurate way to predict since no doctor can precisely pinpoint when you ovulate unless you are currently ovulating. I'm not sure so why so confused if the dates match? Really due dates mean absolutely nothing anyway. U/S will give them a more accurate date, but until that is performed your last period is the only thing to go by.


... - October 14

I answered you on the general pregnancy questions board...


Ashley - October 14

lol, I don't know why. my last period was the end of April . . . but I didn't get preggo until mid - June!!! The pregnancy showed up the end of June. I am so irregular! I just feel blessed to be pregnant, you know? I'm only 23 and I'm due the end of Feb! :)


Beth - October 14

Ashley-I"ve always been so irregular too, they asked me when my last period was and I didn't know! I'v enever kept track because it's never the same day of the month! But now, I'm pregnant, due at the beginning of Feb!


bec - October 16

they go by the last normal period cause thats a pretty good indication that you definitely WEREN'T pregnant then.


Tamara - October 18

My dr said it's because everyone ovulates at different times after their period so it gives them a good ESTIMATE of when you'll be due. The 18-20 weeks u/s gives them more accurate dating.



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