I have gone over this over and over, I am a Health Care Specialist in the Army. And I am very confident in my work and calculations. I have the due date as June 25th,2012. That I received at the 21 week ultrasound. Her first due date was based of her LMP, which I believe was the 19th of Sept. But even then they put it at June 24th. I ask because the paternity of the child is in question, so I would like have the best estimated dates of conception. I believe she conceived in late SEPT, to early OCT. And if that is true, then there is no doubt that I am the father. I would just like to get an OBGYN's take on when she most likely conceived. I know the due date is pretty close, because she was 12w1d on December 13th, which would put conception on Sept 19th. But I know that is just a "wing it" estimate, based on her LMP.

We don't have an OBGYN on the board, but many others can help with your question.

It would be unlikely that she conceived on Sept. 19 if that is when her last period began, but conception the end of Sept./early Oct. would fit with all of the ultrasound dating... give or take several days as it is not an exact science. Keep in mind that conception can occur a few days after the actual act of sex.