Understanding Potential Pregnancy After Risky Sexual Encounters

Question
Hi catherine, so i have a bit of a dilemenna all based on my stupidity... On the morning of 17th may 2014 i got extremely drunk and ended up having a 1 night stand i do not remember if it was protected or unprotected disgraceful behaviour i know!! On may 22-24 i had sex unprotected with my long term boyfriend.... On may 31st i took a pregnancy test and it showed not pregnant... On june 5th i got extremely bad cramping that lasted for 1 day no bleed just very bad cramping and after that my nipples started to get tender! My periods have always been very irregular and i had recently been on the pill but missed a week at the begining of may! I took a pregnancy test on 26th june and it said i was 3plus weeks pregnant! On july 11th i did an abdominal ultrasound and they dated me at 8 weeks 1 day pregnant puting my conception date at 29th may and my due date at 19th february 2015 at my next scan they put me at 13 weeks and 2 days pregnant puting my conception date at 26th may and a due date at 16th february 2015 in my heart of hearts i believe my boyfriend is the dad your thoughts on this matter would be greatly appriciated!!! Thanks very much

Answer
Hi Elaine,

Your boyfriend is the father without question.  Sperm can only live in the reproductive tract for up to 5 days, so there is no way you could have conceived from that encounter given your ultrasound results.  You also had your ultrasounds at the most accurate time in pregnancy so you definitely conceived near the 26th of May, which fits perfectly with the dates of intercourse with your boyfriend, as you are most likely to conceive from intercourse in the two days prior to ovulation, which is exactly what happened in your case.

Best,
Catherine