This study is based on data from records of the longitudinal epidemiologic Collaborative Perinatal Project. It covers observations of 55,000 women and their pregnancy outcomes from date of registration of the first mother in 1959 thru the last seven-year examination of the last study child who was delivered in September, 1966. Early analysis of certain selected maternal parameters and pregnancy outcomes with reference to congenital heart anomalies, using 112 cardiac cases and matched controls in a subsample of approximately 38,000 pregnancies indicated that there were findings meriting further exploration using the full study sample. For instance, controlling for race and removing cases with known chromosomal aberrations, there were more white mothers in the 30 and over-age group than expected at the .05 level. There also was a greater than expected number of mothers with systemic disease complications and prior pregnancy loss in the cardiac outcome group. A preliminary report of these and other tentative findings was presented in 1965 and 1966. Final correlations using the entire first study singleton cohort are under way.