This descriptive study of sexual behavior and response in 1500 obstetric patients registering for prenatal care demonstrates complex interactions of various sociodemographic factors. Variables most predictive of coital frequency during pregnancy include marital status, gestational age, parity, and race, as well as some unique combinations of statistics. Orgasmic response increases with patient age but lack of understanding of the terminology makes further interpretation unreliable. Dyspareunia is experienced infrequently during pregnancy. When it occurs, it decreases coital frequency in single women more than in married women. Studies examining differences or changes in sexual behavior during pregnancy versus fetal outcome must take into account that factors known to affect fetal outcome are also associated with changes in sexual behavior.