Nothing will happen to a pregnant woman if she has unprotected sex and get sperms inside. During pregnancy, ovaries remain suppressed and there is no ovulation. There is also formation of progesterone plug on the cervix which does not allow sperms to come in to uterus. So, sperms die inside female genitalia during pregnancy.
If you continue to have sex while pregnant (which is fine and great) there is a mucus plug at the top of the cervix that keep everything away from the baby. The sperm is discharged by your body later. Enjoy and congratulations.