Delay in fetal maturation in diabetic and accelerated fetal maturation in hypertensive pregnancies have been reported in the past. The spontaneous activity of fetal nervous system during pregnancy was followed longitudinally in a group of 29 normal pregnancies from 28 x th to 40 x th week of gestation by means of fetal behavioural states determination. 1 F state (quiet sleep) progressively increases from median values of 5.0% to values of 22.5-25% at term of pregnancy. This state represents the positive activity of inhibitory centers has been related to a positive evolutionary process of brain maturation according to preceding experiences conducted on experimental models and preterm babies followed with EEG and direct observation in the early neonatal period. The method of behavioural states determination has been applied to a group of 33 gestational diabetes (GDM) pregnant women followed longitudinally, and a clear reduction of development of 1 F state has been evidentiated, with significant differences (p less than 0.001) at 35-36 weeks of gestation versus the control group. The normal values are reached in concomitance with L/S value of maturity. In 30 pregnant women affected by gestational hypertension (GH) different result are obtained: 1 F state seems to develop earlier, and is increased (p less than 0.001) around 30-32 weeks versus the control group if a fetal growth reduction is present. The value of 1 F behavioural state in the evaluation of fetal condition of pathological pregnancies is discussed.