Expert: Dorothy H, LCCE - 8/1/2009

Question
I'm 37 yo. I gave birth to my first and only child 11.6.07. My question is when did I concieve and when does connception occur? I had sex on 2.4.07, 2.12.07 & 2.14.07. I also had what I thaught was my monthly 2.14.09. I found out 3.19.07, my first ultrasound was 5.9.07 thr dr sais I was 13w4d.  During my amnio my gestational age was 16w1d consistant with 16w5d it said in my medical records. Did I get pregnant on 2.4.07 or 2.12.07

Answer
Unfortunately, a second trimester ultrasound and an amnio can be off by a week, so I can't tell you definitely when you conceived. Second trimester u/s aren't as accurate for dating a pregnancy as an earlier ultrasoind would be, but based on the information you gave, the more likely date of conception was February 12 (or the 14)

As far as when did actual conception occur: sperm can live in the vaginal tract for 3 days (can be up to 5 days) and the egg can live 24 hours.  So if you had sex February 12, you could have ovulated anytime from February 11- February 17, and gotten pregnant from having sex Febuary 12.   

I'm not sure if that's clear or if that answers your question completely.  Please feel free to submit a followup question, but just to let you know, I will be away until next week and won't be able to respond until then.