I have a close friend who just found out that she is pregnant. The first day of her last period was on september 7. Her cycle is an average of 31 days. She had intercourse on the 22nd of September where ejaculation took place inside the vagina and then she had intercourse again on the 28 where ejaculation took place outside the vagina. She said she wasn't feeling right and took an at home pregnancy test (First Repsonse, the ultra sensitive test that can detect the Hcg hormone in urine up to 5 days before the missed period) on the 2nd of October, 5 days after she last had intercourse and it was postive. What's the likelihood that she conceived on the 28? Is it more likely that she conceived on the 22, 23, or 24 of september? I am trying to help her figure out what her due date is. She has taken multiple urine test at the doctors and so far they have come out negative. The nurses said their tests aren't as sensitive as the ones you can buy. She has also taken 10 at home pregnancy tests all positive.