Although there isn’t a direct path from the anus/rectum to the reproductive organs, there is a small chance that you could become pregnant during anal sex. This is because the vagina is very close to the anus. During ejaculation the semen (which is full of live sperm) can spill near the vaginal opening. Millions of sperm are released in this fluid, so if the fluid comes in close contact with the vagina, there is small chance that one sperm could find its way to an egg. If you don’t want to become pregnant it’s best to use a reliable form of birth control.
You should also know that anal sex is risky for the transmission of HIV and other STIs, and condoms should be used 100% of the time!