My girlfriend and I are expecting our first child. We've been given a due date of January 28, 1999. I am not 100 percent sure this is my child. Her last period started about April 19 or 20, and she insists that conception was on either April 22 or 26. But when I calculate back from the due date, I get May 7, so I figure conception had to be more like early May, but I can't recall. The problem is that she had a visit with another male friend on May 8 and 9, and I have reason to believe that he thinks the baby is his. I need to know if I am the father, and I can't resolve the conception date to my satisfaction. I don't know the margin of error of any of these methods of calculating things. Can you give me suggestions on sorting this out?

Craig

Conception would likely occur about 38 weeks before the expected due date. Ovulation usually occurs two weeks after the start of the previous menstrual period. So, in this case, if her menses are 28 days apart, it is most likely she ovulated around May 2-4.

It is highly unlikely that you are the father if your only sexual activity was a week or less from the start of the previous menses. The best way to resolve this is to request paternity testing and seek legal counseling to protect yourself.