We compared associations between five indicators of socioeconomic status (maternal education, paternal education, maternal occupation, paternal occupation, family income) and three reproductive outcomes (low birth weight, small for gestational age, preterm delivery) in a representative sample of US births. We used data from the 1988 National Maternal and Infant Health Survey to estimate odds ratios for relationships between the socioeconomic indicators and birth outcomes, separately by race, after controlling for parity, maternal height, marital status, and maternal age. Nearly all socioeconomic indices were associated with low birth weight among both black and white women. However, there was no consistent pattern between the socioeconomic indices and the other outcomes. Maternal and paternal education levels were the best overall predictors. Magnitudes of association differed between black and white women. To accurately assess the impact of low socioeconomic status on reproductive health, definitions of both status and outcome must be made as explicit as possible.