During the first trimester, women are often exhausted and nauseated. They may be uncomfortable about their changing body and their breasts may be tender or sore. As a result, their sex drive may decrease.
However, during the second trimester, many women become more interested in sex, as they become less self-conscious about their bodies and feel less nauseated. More blood flows to the genitals, which can make touch more pleasurable, although for some women, this becomes uncomfortable. Lubrication may increase during this time as well.
During the third trimester, sex can become quite uncomfortable and couples may need to make adjustments to their sexual activity by changing positions or exploring different ways of being intimate.