Although most women can safely have sex during pregnancy, it can sometimes be sensible to be cautious. If your doctor or midwife identifies risk of possible serious complications in your pregnancy, they will warn you and your partner not to have intercourse:
If you are at risk of giving birth prematurely, you should be cautious and in some cases perhaps avoid intercourse, depending on what your midwife or doctor advises. This advice is often given if you have previously given birth before the 37th week or that you’ve had contractions long before your due date.
Sex is not recommended if there is an unexplained vaginal bleeding, both early (threatened abortion) and late pregnancy (where the placenta is potentially vulnerable).
Shortening of the cervix
If your cervix in previous pregnancies has opened up too early, then sex can pose a risk of miscarriage or premature birth.
Problems with the placenta
If the placenta completely or partially covers the opening to the cervix (placenta praevia) sex can lead to bleeding and premature birth.
If you are pregnant with two or more babies, it may be that the doctor advises you not to have sex in the last part of pregnancy to avoid premature birth. However, there is no research that has shown that there is a correlation between sex and premature birth of twins.
Disease or infection
You should also avoid sex with a partner who may have a sexually transmitted disease. If you become infected, such diseases in some cases can be transferred to the baby with serious consequences.