In a longitudinal study of couples expecting their first child many women experienced a diminished sexual desire, most commonly in the third trimester. Among men it was common only during the third trimester. Decrease in sexual desire influenced sexual frequency and in turn sexual satisfaction. During the first and second trimester there was no relation between the perceived change in sexual desire between women and men. The same was true for sexual satisfaction during the first and third trimester. In women there was a relation between experienced change in sexual behavior during pregnancy and background variables such as age, education, rapport with parents, mood, and worry concerning pregnancy and parturition. This was most marked during the first and third trimesters. In the men, only age, rapport with parents, and worry concerning the fetus were related to changes in sexual behavior.