Ultrasound Accuracy: Tracking Pregnancy with Ultrasound Dates

Question
HI Sara i  a question  on may 18 i went to the doctor and told i was  base on a u/s 5weeks6 day and on june 2 i had another u/s at 7 weeks 6day and on june 15 i had another u/s done and said i was 9weeks and 5 days. the doctor said i concieve around april 22. my lmp was april 8 it last 5days it a regular 28-30 cycle. but the only concern is i had sex with partner 1 on april 12 while my cycle was still on it went off on the 13 of april. i had sex on april 18,22,24 with partner 2 which line up with my lmp and conceive day . do you think its anyway i could have got pregnant by partner 1 while my period was still on are do you agree with the doctor? my due date is januray 13, 2011. and could the u/s be wrong  and i i didnot get pregnant on april 22  how accurate are ultrasounds . i am kind scare because i dont want it to be partner 1 baby i am back with partner 2  and happy thanks. last question when do you think i would of have ovulate ?


Answer
Hi Kim,

It sounds like your conception date is correct but keep in mind all dates associated with conception and due dates are estimations only.  But since you seem to have regular cycles, this along with the first trimester measurements help with determining more accurate dates. Usually you ovulate about 2 weeks after your period starts.  It would be very uncommon to have gotten pregnant while still on your period if you have history of regular cycles.  

Also to keep in mind is once you ovulate, the egg only has around 24 hours to unite with sperm before it will deteriorate, so it does look like you ovulated either the 21st or 22nd.     



If there is any question of paternity however, a paternity test should be done to be 100% sure.


Hope this helps and take care!