During the third trimester, your sex drive can become lower. As your belly increases, the pregnancy weight starts to become a little bit uncomfortable.
This might cause mood changes that influence your libido. Closer to your delivery date, discomforts like haemorrhoids, leaky breasts, varicose veins and a "swollen" vagina and vulva may sap all desire for sex. Also, sexual intercourse at this time could create some false contractions that worry some future mothers.
But, if your doctor hasn't recommended otherwise, sex during pregnancy can be safe and enjoyable. However, if you don't feel up for it, don't try to force anything.
Sex positions to try in 3rd trimester: Girl on top, reverse cowgirl, scissors and sitting.
To avoid: It may be best to not have anal sex. Haemorrhoids are a common problem at this stage of pregnancy, and anal sex could cause rectal bleeding.