The majority of couples can still have sexual intercourse during their pregnancy. Your baby is surrounded and cushioned by amniotic fluid and protected by your uterus and a layer of muscles. And the mucus plug inside your cervix helps guard against infection. It is generally safe to engage in sexual intercourse during the third trimester (week 26 onwards).
It is not safe if you're bleeding or have a placenta that's in front of the baby's head--placenta previa. With placenta previa, if the penis comes in contact with the cervix or you have contractions as a result of an orgasm, it can traumatize the placenta and cause significant enough bleeding that you lose the pregnancy. Also, you shouldn't have sex if your membranes are ruptured (water breaks) because then the baby is no longer protected against any possible infection. It's also risky to have sex if it's early in your third trimester and you're having premature labor or you have a short cervix because an orgasm can stimulate contractions. But if you're having a healthy normal pregnancy there's no risk, though as you get larger, it may be uncomfortable.
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