I had sex with a woman 43 weeks ago she is now heavily pregnant can this baby be mine?

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It is doubtful, since gestation is only 40 weeks.

But the only way to be sure, have a paternity test.

I have just received an answer from you about pregnancy. I had sex with her on 23rd aug 2011 and as of today it is nearly 43 weeks. The baby is due within the next week, can I be sure that the baby is not mine without a paternity test as she will not agree to this. I am 65 yrs old and she is 34

As I said, more than likely no. but there is always room for human error

When I had my daughter, they said I was only 34 weeks along, and got ready for a premie birth, and turns out, she was full term, and they had miscalculated.