As long as your pregnancy is proceeding normally, you can have sex as often as you like...Your developing baby is protected by the amniotic fluid in your uterus, as well as the strong muscles of the uterus itself. Sexual activity won't affect your baby...if you or your partner has an active or recently diagnosed sexually transmitted infection avoid sexual intercourse... And it is adviced to avoid sex during last trimester as there are chances of preterm labour... Good luck.