Circadian Rhythms in the Fetus and Newborn: Significance of Interactions with Maternal Physiology and the Environment

Timing of balanced and precise daily delivery of oxygen, nutrients, hormones, and biophysical cues from mother to fetus is essential for fetal growth and successful transition to extrauterine life. Such timing is provided by an arrangement of biological clocks operating in the mother and fetus. However, adverse intrauterine conditions including effects of altering the photoperiod (chronodisruption) during gestation on fetal growth/development and postnatal physiology may translate into adult disease, in which the role played by fetal circadian system remains unclear. Here we review the development of the circadian system, changes experienced by the maternal circadian system during pregnancy, evidence that chronodisruption during pregnancy has long-term effects on the offspring, and current experimental approaches utilized to investigate these issues. However, we are aware that we are just now obtaining new pieces of information that needs to be broadened and studied searching for a diurnal model more comparable to humans. Physiological and pathophysiological questions related to the mother-fetus pair and neonate in vivo need to be addressed as well as the corresponding consequences in adulthood, with expanded and new techniques: among the latter, effects on the transcriptome, microRNA regulome (miRNome), and proteome of different maternal-fetal, neonatal, and adult tissues.