In the course of the research we assessed the status of the autonomic nervous system and adaptation in infants with intrauterine growth restriction (IUGR) during the first six months of life. We observed infants born after abnormal pregnancies with IUGR (Group I), infants born after abnormal pregnancies without IUGR (Group II) and virtually healthy infants (without pregnancy and labour complications) in Group III. Despite the complicated medical history, at birth Group I infants displayed the

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... vel of sympathetic nervous system activity comparable to the one in Group III infants and lower than the level in Group II infants. However, in Group I infants sympathetic nervous system activity was restricted and compensatory reserves were depleted, sympathicotonia was prevalent. Decrease in frequency of asympathicotonic responsiveness of the autonomic nervous system (from 36.11% to 16.67%) and increase in sufficient adaptation (from 27.78% to 33.33%) in Group I infants by the end of neonatal period of life are related to the treatment of the pregnant women, as we suppose. Despite the fact that by the age of three months the level of sympathetic nervous system activity in Group I infants was lower than that in Group II infants, Group I infants showed less intensive decrease in sympathetic activity level followed by more strain on compensatory reserves. By the age of six months the sympathetic nervous system activity had continued decreasing and was no longer significantly different in Group I and Group II infants. At the same time, Group I infants displayed more frequent hypersympathicotonias combined with asympathicotonic responsiveness of the autonomic nervous system (in 16.36%). The results of the research show that IUGR in infants is connected to high rate of hypersympathicotonia with asympathicotonic responsiveness of the autonomic nervous system, which results in higher frequency and intensity of clinical implications of autonomic nervous system dysfunction.