Behavioural states in the fetuses of nulliparous women.

Behavioural state observations were carried out serially on the fetuses of 14 low risk nulliparae. They were observed serially at 2-weekly intervals between 32 weeks gestational age and delivery at term. Two real-time ultrasound B-scanners were used to visualize fetal body, eye and breathing movements. Fetal heart rate patterns were recorded simultaneously by means of a clinical fetal monitor. States appeared to be present transiently in three fetuses at 34 weeks. States were definitely present in five of 13 fetuses studied at 38 weeks and six of seven observed at 40 weeks. In comparison to the fetuses of low risk multiparae studied earlier, the fetuses in the present study showed a somewhat lower proportion of quiescence (coincidence 1F) and higher percentage of activity (coincidence 2F); however, most of these differences were not statistically significant. In the fetuses which showed states, the distribution and durations of the states at 38 and 40 weeks were not different from those found previously in the fetuses of multiparae. We conclude that the development of behavioural states is generally similar in the fetuses of low risk nulliparae and multiparae, but that states appear at a somewhat later gestational age in the fetuses of nulliparae.