OBJECTIVES: In general, epidemiological studies have evaluated cases with congenital cardiovascular abnormalities together. The aim of this study is to describe the birth outcomes of cases with isolated/single atrial septal defect type II (ASD-II, i.e. only a fossa ovalis defect) after surgical correction or lethal outcome in the light of maternal sociodemographic data. DESIGN: Comparison of birth outcomes and maternal characteristics of cases with ASD-II and controls without defect. SETTING: The population-based Hungarian Case-Control Surveillance of Congenital Abnormalities. POPULATION: Hungarian newborn infants with or without ASD-II. METHODS: Medically recorded birth outcomes, maternal age and birth order were evaluated. Marital and employment status was based on maternal information. The lifestyle factors were analyzed in a subsample of mothers visited at home based on a personal interview with mothers and their close relatives, and the family consensus was accepted. MAIN OUTCOME MEASURES: Mean gestational age at delivery and birthweight, rate of preterm birth and low birthweight, maternal age, birth order, marital and employment status. RESULTS: The evaluation of 471 cases with ASD-II and 38 151 controls without any defects showed a female excess in cases with ASD-II, having shorter gestational age and lower mean birthweight, and thus a higher rate of preterm births and low birthweight. CONCLUSIONS: Intrauterine growth restriction and shorter gestational age were found in cases with ASD-II, particularly in female children. These factors may have a general developmental process in which there was not closure of the foramen ovale, thus echocardiographic screening of these babies might be of value.