Prognostic value of the indexes of the regulation of cardiothorrh of the mother and fetus in the outcome of the gestational period and childbirth with the deficiency of the body weight of the pregnant woman. Objective – to study the prognostic value of the indexes of the regulation of cardiorhythm of the mother and fetus in the outcome of the gestational period and childbirth with a deficiency of the body weight of the pregnant woman. Material and methods. A survey of 50 pregnant women with a deficit of body weight and their fetuses (the main group) was carried out. The comparison group consisted of 50 pregnant women with normal body weight and their fruits. Neurovegetative regulation of the heart rhythm of the mother and fetus was studied by the method of spectral and mathematical analysis of heart rate variability. Results. The state of the regulatory processes in the mother-placenta-fetus system, revealed on the basis of CIG, has a prognostic value in the outcome of pregnancy and childbirth for the mother and fetus. The most prognostically unfavorable is the hypoadaptive state, as well as the phenomenon of «energy fold» and «functional rigidity» of the mother. The hyperadaptive state of the mother is more prognostically more favorable, however, in comparison with the norm-adaptive state, the frequency of obstetric and perinatal complications is also higher. Violation of the regulatory processes in the fetus was also manifested in the high frequency of the pathological course of the postnatal period in the newborn, especially in the hypoadaptive state. The most favorable outcomes in the early neonatal period, when discharged at home, had a group with a norm-adaptive state of the fetus during pregnancy. Field of application. Problems of correction of obstetric complications during pregnancy and childbirth, especially of severe forms, represent one of the most important problems of obstetrics. One of the possible directions for the definition of medical tactics is the approaches based on the study of regulatory and adaptive processes in a single mother-placenta-fetus system, and their control in the course of treatment. Such possibilities are a non-invasive method of cardiointervalography of mother and fetus, conducted simultaneously. Conclusions. The state of regulative and adaptive processes of mother and fetus in pregnant women with deficiency of body mass is characterized by various forms of disorders. For the outcome of pregnancy and childbirth, the hyper-and hypo-adaptive state, the phenomenon of «energy fold» and «functional rigidity» in the mother, the fetus is hyper, hypoadaptive, is unfavorable. The norm-adaptive state of the regulatory processes in the mother and the fetus provides favorable outcomes of pregnancy and childbirth.