Diabetes is a metabolic disorder that complicates pregnancy. Early detection of patients at risk of developing complications is particularly important. Failure of normal cardiovascular adaptation that takes place in pregnancy has been associated with poor perinatal outcome in preeclamptic patients. The aim of this study was to investigate if complications were higher in diabetic patients with cardiac maladaptation. Fetal, uteroplacental Doppler and echocardiographic examinations were performed once in the second and third trimesters in diabetic and healthy pregnant patients. Physiological cardiac hypertrophy was apparent in healthy patients. This, although within normal limits, was less prominent in patients with diabetes. The majority of patients were found to have normal Doppler waveforms. The abnormal uteroplacental flow group consisted almost entirely of patients with pregestational diabetes, especially type I diabetes. Neonatal complications were most common in this group. No relationship was found between echocardiographic findings, Doppler waveforms and poor perinatal outcome.