Understanding Due Dates: Conception, Ultrasound & Estimated Delivery

Question
Thanks for the helpful information.  I did fail to mention that my intial EDD was April 20. I knew that was b/c of LMP. However i know a woman is "usually" ovulating 12-14 days after their period. For me that would have been 7/26 - 7/29. As I said I did have sex on 7/27. The intercouse on 7/22 though unprotected, resulted in NO ejaculation (not in me for that case). When tranferring doctors the baby measured for a due date of 4/15/07 when I was 16wks. The next check-up measured him at a EDD indicating 4/18/07. The fetal specialist's measurments were 1 day ahead of the 4/18 due date. Thus resulting in my confusion about the ultrasond. How accurate are these readings? Are they based on averages? Could I have possibly ovulated only 7 days after my period?

Answer
The readings are based on averages. How accurate they are often depends on a dash of luck and the skill/experience of the doctors or specialists doing it. There is some fluxuation but that is to be expected. However, even with the fluxuation they're all agreeing with the general two to three-day span which is encouraging. Is it possible you ovulated a week early? Yes, though its kind of a long-shot. Also keep in mind that pre-ejaculate can contain viable sperm as well. However, if you had unprotected sex on the 27th, I would put that as a much higher chance of the encounter that got you pregnant than the encounter on the 22nd. Either way, it's too close to call and at this point I recommend just relaxing and not worrying about it until you get the paternity test. I would recommend informing the gentleman with whom you had the encounter with on the 27th.

Best wishes,
Helen =)