PRIMATE PARTURITION AND THE ROLE OF THE MATERNAL CIRCADIAN SYSTEM

Several 24-h rhythms have been observed in the mother and in the fetus during primate gestation. In the mother, 24-h rhythms occur in biophy sical variables, pregnancy-associated plasma hormones and preparturien t myometrial activity. In addition, both pregnant non-human primates a nd pregnant women deliver preferentially during the night and early mo rning hours. A crucial question pertaining circadian rhythms is whethe r 24-h rhythms that may be observed during pregnancy are endogenous in nature and entrained by the light-dark cycle or whether the daily pho toperiod is a causal stimulus. Our work has addressed the role of the maternal and fetal circadian system for 24-h rhythms in pregnancy-asso ciated maternal plasma hormones, preparturient myometrial activity and parturition in human and non-human primate pregnancy. In the present review, the results of some of our studies are being discussed in comb ination with data available from the literature. It is apparent that 2 4-h rhythms that may be observed during primate pregnancy are determin ed by the maternal circadian system, suggesting that the developing fe tus receives information about the ambient time of the day via the mot her. Fetal entrainment by the mother may ensure fetal cooperation so t hat parturition occurs at the most favorable time of the day. We concl ude that the functioning of the maternal circadian system is integral to the pregnant state. Thus, proper care and management of pregnant wo men and the ultimate outcome of obstetrics may benefit from more timel y methodologies. A chronopharmacological attitude towards the preventi on of premature labor and the induction and augmentation of labor at t erm may yield new therapeutic strategies. Such an approach will enable delivery to take place under optimal conditions for mother and child.