We examined medical obstetric conditions predating pregnancy and current symptoms as predictors of the timing of the start of prenatal care among low-income women in Snohomish County, Washington. The investigation was a cross-sectional survey with retrospective record review. Subjects were 473 women who sought care through the community health center network, which was the only provider of prenatal care for low-income women in the county at the time of the study. Women with a history of two or more medical or obstetric conditions were more likely than those without such histories to seek prenatal care early in pregnancy. Women who, in the current pregnancy, had few physical symptoms were more likely to delay seeking prenatal care than symptomatic women. Among this relatively homogeneous group, sociodemographic characteristics were not associated with the timing of entry into prenatal care. The findings help to explain the patterns of prenatal care use of certain groups, and suggest avenues for intervention to improve use among low-income women.