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Had sex and took prenatal vitamins. Done with ultrasound test. Is paternity test required?

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Practicing since : 1997
Answered : 1031 Questions
I have a question about the accuracy of ultrasound for conception dates.

I had sex with Partner A once in the late night XXXXXXX 18/early morning XXXXXXX 19. used a condom, and took the morning after pill within 50-55 hours (was also on birth control - but take it inconsistently). XXXXXXX 18 was also the last day of my period according to my birth control pack, but I cannot remember if I actually had a period.

I was with Partner B end of XXXXXXX - present. I had what I believe to be a LMP on Feb 5. I went off birth control at this time & started taking prenatal vitamins because we decided we wanted to try for a baby. On March 6 I found out I was pregnant by a FAINT line on a hpt. The same day I went to the OB, and my urine test came up negative. They gave me a blood test & it was positive.

My first ultrasound was on 4/1. It was performed ABDOMINALLY, therefore I am not sure of its accuracy. It stated that was 7w0d with an EDD of 11/18. I had another ultrasound on 4/26 (abdominally) stating 11w,3d EDD 11/12 CRL 45mm. Another ultrasound on 5/14 dating 14w,1d EDD 11/11 CRL 82mm. Ultrasound on 6/18 dated 19w, 0d EDD 11/12. Ultrasound 7/5 dated 21w, 2d EDD 11/13. Last ultrasound on 8/12 dating 26w,6d EDD 11/12.

My question is is possible that I got pregnant from the XXXXXXX 19 encounter. Is a paternity test necessary to determine this with certainty? I am just nervous about the accuracy of an early ultrasound performed abdominally.

Also would the morning after pill still have been effective if taken 50-55 hours after the encounter?
Posted Thu, 19 Sep 2013 in Pregnancy
Answered by Dr. Kulsoom Qureshi 6 hours later
Brief Answer:
Early ultrasound is very reliable

Detailed Answer:
Thanks for your question.
Morning after pill can prevent 86 % of expected pregnancies, if taken within 72 hours of UNPROTECTED intercourse. In addition, you were on birth control pills & used condom as well. Also, This was the less fertile time of your cycle.
Ultrasound done in the first trimester is very reliable to date a pregnancy even if it is done abdominally.
Considering all these facts in mind, this is quite unlikely that you were pregnant before Feb 5, unless you have some doubts about the accuracy of dates mentioned, or if there is history of intercourse with partner A after XXXXXXX 18/19.
So, I don't think if these facts are true, paternity test is required.
Wish you good health.

Above answer was peer-reviewed by
Follow-up: Had sex and took prenatal vitamins. Done with ultrasound test. Is paternity test required? 2 days later
The XXXXXXX 18 encounter was a one time event & was protected on top of taking Plan B. so just to clarify you think that the XXXXXXX 19 encounter is ruled out? I have had multiple ultrasouds that line up, so wouldn't that prove accuracy since they show the same date?
Answered by Dr. Kulsoom Qureshi 9 hours later
Brief Answer:
I admitted that early ultrasounds are reliable

Detailed Answer:
Yes, with the given details it is next to impossible, that your January 18 encounter could have caused this pregnancy.
I have already appreciated the accuracy of your ultrasounds in favor of your second partner being the father of this pregnancy.
Have a nice day.
Best wishes.
Above answer was peer-reviewed by
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