Abstract
Background: Under normal circumstances, change in heart rate variability (HRV) in pregnancy projecting alterations within the regulation of the autonomic nervous system (ANS). Many previous works have shown an impact of gestation on the role of ANS in control of heart rate in the western country; however, it is poorly understood in Indian population, but then again a definitive this study is beneficial in relating to the influence on maternal autonomic cardiovascular control in some aspects of physiology in normal pregnancy.

Aims and Objective: The aim of our study was to analyze the cardiac autonomic control throughout different stage of pregnancy with HRV.

Materials and Methods: This study (n = 200) comprised normal non-pregnant and pregnant participants in the age of 20–30 years old, were divided randomly into Group 0 (n = 50) - control group comprised non-pregnant, healthy women. Study group (n = 150) classified into three subgroups; Group 1 (n = 50) - participants in their first trimester, Group 2 (n = 50) - participants in their second trimester, and Group 3 (n = 50) - participants in their third trimester. The electrocardiographic R-wave-R-wave interval HRV was measured on a beat-to-beat basis with the help of an electrocardiogram machine (BPL Cardiart 1087/MK-V) for 5 min.

Result: Mean RR interval was decreased significantly in the 3rd trimester of pregnant study group when compared to non-pregnant control groups. Root of the mean of the sum of the squares of differences, NN50, and pNN50 were increased significantly in the first trimester of the pregnant study group when compared with non-pregnant control groups. Low frequency (LF) and LF (nu) significantly decreased, high frequency (HF) and HF (nu) significantly increased in the 1st trimester and significantly altered in 2nd trimester as well as 3rd trimester as vice versa. LF/HF ratio was significantly decreased in the 1st trimester and significantly increased in the 2nd trimester as well as 3rd trimester of pregnant study group when compared to non-pregnant control groups.

Conclusion: The cardiac autonomic nervous activity in pregnancy showed a higher parasympathetic dominance in the 1st trimeste r and decreased gradually in 2nd trimester as well as 3rd trimester, and there was a lower sympathetic activity in the 1st trimester and increased gradually in the 2nd trimester as well as 3rd trimester. These changes throughout normal pregnancy may have an advantage in the initial identification of abnormal physiological function.

Key words: Heart Rate Variability; Pregnancy; Sympathovagal balance; Low/High Frequency