The purpose of this study was to find out possible differences in prenatal diagnosis (PD) by amniocentesis or chorionic villus sampling and ultrasound examination before 16 weeks' gestation (early ultrasound examination, EUE), according to area of residence and level of education of the mothers. Data come from a multicentre study in Italy involving 43 maternity hospitals (Mercurio project) and were collected through structured interviews a few days after delivery. Study subjects were 1541 mothers of single non-malformed infants born between April 1992 and March 1994. Overall, the incidence of PD and EUE was 5.8 and 80 per cent, respectively. After adjustment for maternal age and other possible confounders, the odds ratios for PD were 2.19 (95 per cent confidence interval (CI) = 1.26-3.81) when women residing in the northern regions were compared with those residing in the southern regions, and 2.06 (95 per cent CI = 1.12-3.79) and 4.08 (95 per cent CI = 1.97-8.42) when women with medium and high levels of education were compared with those with low level. For EUE, the odds ratios were 1.77 (95 per cent CI = 1.32-2.36) and 2.88 (95 per cent CI = 1.56-5.29) when comparing women with medium and high levels of education with those with low level. No relationship was found between area of residence and EUE. These geographical and social inequalities in prenatal care in Italy should be taken into account for the organization, delivery, and evaluation of pregnancy services in the coming years.