Interaction between the circadian clocks of mother and fetus.

In mammals, a unidirectional communication exists between the biological clocks of the mother and fetus. As a biological clock begins oscillating in the suprachiasmatic nuclei of the fetus, redundant circadian signals entrain the fetal clock to the prevailing light-dark cycle. Recent studies have revealed an activatable dopamine system within the fetal hypothalamus which may serve as a final common pathway by which maternal signals entrain the fetus. An entrained biological clock during fetal life makes the developing mammal better prepared for life in the outside world.