Summary of nonlinear models 1, 2, and 3.

Source: Collaborative Perinatal Project (CPP).Notes: Model 1 includes the following covariates: mother's age, father's age, child's age, getstation weeks, child's sex, mother's race/ethnicity. Model 2 includes those covariates plus mother's marital status, family's socioeconomic index, and mother's and father's past mental illness (indicator variables). Model 3 includes those covariates plus mother's and father's education, total number of siblings, and birth weight.