To investigate the effects of diazepam on fetal heart rate and Apgar scoring administered intravenously during the active phase in labour, sixty-two normal term parturients during the active phase of labour with the cervical dilation to 3-5 cm were randomly divided into two groups, diazepam group (n = 32) and control group (n = 30). In diazepam group, 10 mg diazepam was administered intravenously. The concentrations of diazepam in maternal and cord serum were measured by high performance liquid chromatography after birth and the fetal heart rates were monitored by electronic monitor before or after administration of diazepam and Apgar scores were determined immediately after birth. The results showed that the mean level of diazepam in umbilical cord serum was markedly higher than that of maternal serum. Fetal heart base line mutation in diazepam group was weaker than that of the control group. Apgar scores in the neonates of diazepam group was lower than those of the control group. The results indicate that the use of diazepam in pregnant women during active phase of labour may cause depression of fetus.