Expert: Dorothy H, LCCE - 9/28/2010

Question
My lmp was june,24th 2010 ,i have regular 28 day cycles. i am 13 weeks 5 days  pregnant today actually , i have had three early ultrasounds and the dates given by the ultrasounds all match up exactly to my lmp on june 24th, here is my problem , on june 14h me and my boyfriend were on a break and i had sex with my ex i then got what i think was my period on june 24th. and me and my current boyfriend worked things out , so i guess you can say sex with the ex on the 14th was a one night stand. so me and my current boyfriend wanted to coneive, all my ultrasounds match up to my lmp of june 24th . so if i am 13 weeks 5 days  pregnant now , by ultrasound and lmp does that mean i conceived 13 weeks 5 days  ago? or are they going by gestational age(lmp)..so does that mean i actually conceived 11 weeks 5 days ago but thats how ultrasound measures?(which by gestational age calculators say i conceived between july 6-9th) ) is there ANY possible way the my ex is the father? or is my boyfriend the father? how do ultrasounds measure..by gestational age(l,p)? did i get pregnant after my period!?(which my period came when it was supposed to and about 7 days long... please help!!!!

Answer
Hi Emmah,

I did answer this question for you already, but in case you didn't see the answer, here it is, adjusted for the details in your current question:

When they say you are 13 weeks 5 days, they are going by your LMP, not actual gestational age.  So when you are 13 weeks 5 days pregnant, it means that you actually conceived 11 weeks and 5 days ago, NOT 13 weeks and 5 days ago.  It is very confusing, I know!

With three ultrasounds lining up with your LMP, there is absolutely no way that you conceived June 14.  If you had, your ultrasounds would have shown a much more developed fetus. Your boyfriend is the father.

Sincerely,

Dorothy H, LCCE