The aim of the study was to evaluate the sexual functions during pregnancy using the Female Sexual Function Index (FSFI) questionnaire. Pregnancies were recorded in a prospective cohort study comprising 40 healthy pregnant women. Pregnant women who had a stable relationship with their partner were enrolled in the study when were first diagnosed to be pregnant. During their antenatal visits, subjects were asked to complete the FSFI questionnaire and other information about their sexual life in each trimester. Each FSFI domain score was calculated and mean scores in each domain were compared according to the trimesters of pregnancy. Data of 37 subjects for the first, 36 for the second and 34 for the third trimesters of pregnancy were eligible for the analysis. The mean age was 25.5+/-4.5 y; mean parity was 0.4+/-0.7 and mean gravity was 1.6+/-0.9. The frequency of intercourse attempts during the last 4 weeks was 8.6+/-3 before pregnancy, and 6.9+/-2.5, 5.4+/-2.6 and 2.5+/-1.4 in the first, second and third trimesters of pregnancy, respectively. In all domains of FSFI, significant decline in domain scores was determined during pregnancy. The comparison of satisfaction and pain domain scores between first and second trimesters showed significant differences. All of the domain scores significantly decreased in the third trimester of pregnancy. Our results showed that sexual functions are significantly decreased during pregnancy and worsen as the pregnancy progresses. Childbearing couples should be given information about the sexual problems and fluctuations in the patterns of sexuality during pregnancy.