The Canadian Medical Association Journal has published a new primer designed to help physicians when they counsel pregnant women. They note that sex during pregnancy is normal and is generally considered safe. The authors point out that there are very few proven contraindications and risks regarding intercourse in normal pregnancy.
Pregnant women and their partners are often afraid to have sex. Men may think they are "invading" the home of the fetus and could actually harm the baby. In fact, the fetus is quite safe, ensconced in the uterus (womb), and the cervix (opening of the uterus) is closed in normal pregnancy. The penis has no contact with the fetus or the uterus during normal intercourse, no matter what the position.
When is intercourse considered risky? Only for women who are at high risk for preterm labor and for those with placenta previa, because there is increased risk for hemorrhage. Even women who have had preterm labor may safely have sex unless they have cervical incompetence or a lower genital tract infection.
Women who are under the care of an obstetrician should know if they have any of these risks. The vast majority of women should be reassured that sex during pregnancy is safe for mom and baby.