Can I get pregnant if I have sex a day before my periods?

DR, I had sex and the next day I had my period. What surprises me is that that was the only time I had sex and yet now I have missed my period. I took a pregnancy test and it came out positive. How could it have happened? Alicia

Many women think any vaginal bleeding is their periods and if they are using fertility awareness to avoid getting pregnant, they are likely to end up getting an unwanted pregnancy. Women may bleed for a day or two at the time of ovulation. Having sex before or after the bleeding can lead to unwanted pregnancy.

Women with irregular or abnormal periods may get pregnant even when they are bleeding if they have sex then. A woman’s normal periods happening from 21-35 days with the average being 28 days may last two to seven days and the egg lasting up to 24 hours. Ovulation happens 14 days to the next period meaning that a woman with a menstrual cycle of 21 days can ovulate during her seventh day of her period and can get pregnant if she plays sex in her periods. Pregnancy happens when sperms fertilise the eggs in fallopian tubes and the fertilised eggs then get implanted in the womb. The sperms have to swim from the vagina where they are deposited to the fallopian tubes to fertilise the eggs with the fastest swimmers taking as little as 45 minutes to reach the tubes.

Ugandans when they have had unprotected sex and fear getting pregnant instead of using emergency contraception will instead take anything rumoured to cause uterine bleeding purportedly to flush out sperms (or a fertilized egg) to avoid pregnancy.
Bleeding from the womb a day after sex will neither eliminate the sperms nor the fertilised eggs tucked away in the fallopian tubes.