Expert: Dorothy H, LCCE - 2/13/2011

Question
QUESTION: I am currently 31 weeks pregnant. My due date is on march 18. Ive been wit my boyfriend since june 1st and i was with another man only on june 12th i know thats horrible. Is there any chance the other man could be the father?

ANSWER: Hi Ariana,

Going by your due date, it looks like you got pregnant around June 25 (give or take a few days)  If your due date was confirmed by ultrasound in the first trimester, it is almost 100% that you did not get pregnant on June 12.  

If you did not have a first trimester ultrasound to confirm your due date, it is still very unlikely that he is the father, especially if your cycles tend to be regular.

I hope that helps!

Sincerely,

Dorothy H, LCCE

---------- FOLLOW-UP ----------

QUESTION: its me again! okay well at my 25 week ultrasound they said i was 2 weeks further along judging by the size of the baby. My period is very irregular. Does this change anything? Thanks so much you been a great help.

Answer
Hi Ariana,

As an ultrasound at 25 weeks can be off by up to 2 weeks, it's not going to be very useful in predicting the date of conception.  After the ultrasound, did they move your due date to early March?  If they kept your due date the same, then your doctor is not trusting the accuracy of the ultrasound in dating the pregnancy.

It looks like you got your LMP on June 11.  The odds that you would conceive the day after your LMP are very low, no matter how irregular your period is. However, if you had another period at the end of May, then that does make it more likely that the June 11 period wasn't really a period and unfortunately increases the chances that you got pregnant on the 12th.