Behavioral states in the human fetus.

Simultaneous use of real-time ultrasonographic scanning and cardiotocography has demonstrated that the human fetus exhibits well-developed behavioral states from about 36 week's menstrual age onward. Four states have been identified that are very similar to states that have been described in neonates of equivalent age. Prior to 36 weeks, cycles are present in the state variables individually: however, these cycles are not synchronized. The implications of the alternation of behavioral states in the fetus for antepartum assessment of fetal condition are discussed.