Comparative study of Heart Rate variability in pregnant women living in conditions of High-mountain Hypoxia of the Pamirs and the steppe zone of Central Kazakhstan

Abstract

A comparative analysis of the main indicators of heart rate variability was carried out in 72 women aged 25-35 with a normal course of pregnancy, 90-30 days and 10-5 days before delivery, living in different geographical areas: high-mountainous region of Tajikistan (Pamir, Murghab village, 3600-4200m above sea level) and the steppe region of Central Kazakhstan (546m above sea level). The mechanism of compensatory-adaptive reactions, which is not typical for other regions, was revealed in pregnant women living in conditions of high-altitude hypoxia. In women living in the territory of Central Kazakhstan, at 90-30 days before delivery, pregnancy proceeded against the background of increased activity of the sympathetic division of the autonomic nervous system (SD of ANS). Recovery of heart rate variability (HRV) began 10–5 days before term birth, which is the result of a decrease in the effectiveness of adrenergic effects and an increase in the effectiveness of M-cholinergic effects on heart rate, according to some authors1,2. These changes in HRV can be successfully used as a biological marker of a mother’s readiness for childbirth, taking into account the availability and safety of the HRV method. In Pamir women, an increase in the activity of the parasympathetic division (PD) of ANS was noted 90-30 days before childbirth, and persisted until delivery. Starting from the third trimester of pregnancy, the dynamics of the values of such parameters as AMo (amplitude mode), ARI (autonomic rhythm index), RMSD (root mean square deviation), VR (variation range) showed a optimal functional state of regulatory systems before childbirth. This was also evidenced by the value of the stress index, which was in the range of 194-197 units. This mechanism of regulation in the conditions of high-altitude hypoxia ensures the normal development of the fetus and the mobilization of the functional reserves of newborns during childbirth and after birth.