A member asked:

Hello i cheated on my boyfriend now i'm trying to figure out when i conceived. i'll be 21 weeks pregnant saturday. due date april 18th by,ultrasound.

2 doctors weighed in across 2 answers
Dr. Gerard Honore answered

Specializes in Fertility Medicine

How accurate?: is your due date/gestational age? When did your last period start? If you're not sure, how was it calculated? From 1) First trimester ultrasound? 2) Second trimester ultrasound? If your EGA is exact you conceived very close to July 24-26, 2014. Are your periods regular? 1st trimester US is +/- 3 days, 2nd trimester not as good. Hope this helps!

Answered 8/9/2015

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Paternity test: This due date would have ovulation on July 27 and implantation on August 3 but there is a margin of error (+/- days) in the ultrasound and this is based on an ideal 28 day cycle. In addition, both sperm and eggs live in the reproductive tract for awhile so intercourse and conception don't necessarily occur on the same day. A paternity test is the only sure way to know who is the father.

Answered 12/5/2014

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