Can you determine paternity by dates?

Full term gestation of a fetus ranges from 38 to 42 weeks. Doctors primarily suggest 40 weeks in the EDD (estimated date of delivery), but a woman, especially first time mothers, can go into labor two weeks early or two weeks late of her EDD. However, if a woman appears that she will not go into labor after more than 42 weeks, or if the baby is already getting too large earlier than 40 weeks, the doctor will induce labor. That is the number they shoot for.

In any case, the best way to confirm paternity is a DNA test post-partum.