The effects of corticosteroids, given for enhancement of fetal lung maturation, on fetal heart rate (FHR) are controversial and may decrease its variability. FHR patterns were analyzed by computerized cardiotocography in 46 fetuses from 23 normal dichorionic twin pregnancies on days 0, 1 and 4–7 while the mothers received four intramuscular injections of 3 mg betamethasone sodium and 3 mg betamethasone acetate within 48 h to enhance fetal lung maturation. Compared with pretreatment values, FHR showed a decrease in long- and short-term variations; other parameters, e.g. the number of fetal movements, remained unchanged. However, decreased FHR variation was followed by an increase in the acceleration rate after maternal administration of betamethasone. These modifications were transient and should not lead to unnecessary anxiety or intervention in otherwise normal fetuse