Can you get pregnant during your period?

Patient's question:

I had sex with my girlfriend after which she had blood clots in the toilet. Those days she was also having her period and she didn't know if I came inside. She said her period wasn't over yet. Can I get pregnant in this situation? If it's 3-4 days after her period, can I get pregnant? Thank you

Doctor's answer:

The first reason why sexual intercourse should be avoided during menstruation is to prevent reproductive system infections. When women experience menstruation, the endometrium (the tissue lining the inside of the uterus) peels off in pieces. During menstrual intercourse, it is very easy for bacteria from the surrounding area of the vulva and perineum (the area between the vaginal opening and the anus) to be introduced into the vagina, cervix, and even the uterus. Bacteria thrive and multiply in the presence of blood, leading to local inflammation known as endometritis. This condition not only causes fever and lower abdominal pain but also results in...