Has anyone had sex the day before their period & gotten pregnant?

Unless you have really short cycles, it is unlikely that you would get pregnant the day before your period. Spending lives up to 5 days inside the body, and you will need to have ovulated to have produced an egg. Ovulation generally happens mid cycle, though that can vary. Your period happens when the egg has not been fertilized, and you are expelling the product of the non-pregnancy. You'd need to have a seriously short cycle to make that happen (not saying that you could have a short cycle; it would just be unusual). In order to be fertile, you need about 2 weeks in between your ovulation and your period (the luteal phase). Shorter luteal phases are not generally favorable for pregnancy. Since pregnancy is always a possibility (no matter how faint), it is advisable to use birth control if you are not trying to conceive. If you ARE TTC, having sex before ovulation is your best chance!

So I had a situation where it's possible that I got pregnant the day before my expected period. I believe I had an anovulatory cycle (no egg), followed by my normal cycle (ovulation CD8) with no period in between. Due to the way this happened, it was like my positive test was 13 days after my period was due. At my first ultrasound the baby measured 4 weeks smaller than expected (measured 6wks at 10wks), and then I miscarried 2 weeks later.