Human biorhythms display the adaptation of living organisms to the external environment. These are mechanisms that are so well-regulated by nature that they are often called ‘biological clock’.There are definite functions in the body of the newborn that have a daily rhythm (with a period of 2 to 25 hours). Such a rhythmic setup depends on the maturity of the newborn: the circadian rhythm of melatonin synthesis in humans arises from the first days after birth, and its formation ends up 9-12 weeks and in premature babies for 2-3 weeks later. The development of the ‘biological clock’ of the newborn is significantly influenced by the conditions of the environment. Melatonin provides recovery, stabilization and synchronization of chronorhythms of different frequencies, including daily periodism.At this rate, the pleiotropic effects of melatonin on the control of biological rhythms during this period are a matter of particular attention. Our reference is devoted to it.During early postnatal adaptation, it is reasonable to determine the biorhythmologic features of the main physiological indicators of life: hourly blood pressure, heart rate and respiratory movements, body temperature, cortisol, adrenaline, norepinephrine, 6-sulfatoxymelatonin (melatonin metabolite) in fractional urine in the dynamics of the early neonatal period.The tasks of chrononeonatology are the study of the peculiarities of the formation of the circadian setup of physiological functions and the level of the main adaptive hormones in the dynamics of the early neonatal period.In the prenatal period, melatonin penetrates the fetus from the pregnant woman through the placenta, and after birth it enters the baby's body with the mother's milk. It is believed that periodic signals emanating from the mother's pineal gland (PG) cells synchronize the fetal chronorhythms. In the early stages of embryogenesis, these signals have a nervous and humoral genesis, and after birth, only humoral influences.The concentration of melatonin in the blood of a pregnant woman reaches a maximum level to the 32nd week of pregnancy and is restored by the 2nd day after childbirth.Fetal growth restriction is due to a significant decrease in the secretion of melatonin during the first 3 months of life of newborns. It is important that in the preterm infants, the relative deficit of melatonin lasts from 2-4 to 7-8 months.Maternal influence on development does not end with delivery, but continues in the neonatal period. Breast milk contains more than 60 biologically active substances (STH, lactogenic hormone, IGF-1, insulin, etc., in particular melatonin), whose level significantly exceeds their concentration in the peripheral blood of the mother.Early breastfeeding, the rooming-in in the postpartum period, an arbitrary feeding regime contribute to the earlier formation of biorhythms of physiological indicators of life and the favorable course of adaptive processes in newborns.So, summing up, we note that the child's condition is associated with an adequate biorhythmic daily activity. Metabolism lability in the newborn requires keeping in mind the structure of biorhythms in the postnatal period to prevent the development of morbid conditions.
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