Paternity Determination with Irregular Periods: A Guide

Question
Hi! Before i had my daughter last year i had an irregular period.  I had a period 12/11/10 and didnt have another until 2/2/11. I had protected sex with one man on 3/3/11 but had unprotected sex with another on 3/6/11... I also had protected sex on 3/20/11.. my due date was 12/6/11; but i had her on 11/23/11. How do i figure paternity??

Answer
Hi there Tiff,

As you can imagine, it's a bit tricky trying to pin down paternity based on dates alone when you have irregular periods. However, I would estimate that the man from 3/20/11 is the father. I am basing this on your due date--as this is a clearer reflection of conception than your delivery date.

Depending on when your dating scan was, it would have had accuracy of +/- 3days. Your EDD includes the first day of your last menstrual period. In women who have regular periods, this would usually include the 2 weeks up to the date of conception. As your periods are irregular, so are your ovulation dates. I am going on quite rough biological calculations here, but I do believe the man from the 20th would be the most likely.

All the best,

Laura