Umm, why would sperm be bad for a baby?

Lol. It's okay to have sex when you're pregnant. He can ejaculate inside you all his little heart desires. The baby is safe in your uterus. It's sealed off.

If your cervix was open you would not be pregnant therefore it means that almost nothing can enter the uterus and last I checked your baby is in there. A little research on pregnancy would do you wonders.