Heart rate variability is reduced in normal pregnancy irrespective of trimester: A cross-sectional study from Gujarat, India

BACKGROUND: Pregnancy is associated with profound cardiovascular adaptation with altered cardiac autonomic balance. It can be studied by heart rate variability (HRV) which indicates beat to beat RR interval variation on ECG. OBJECTIVE: We studied 5 min HRV in normal pregnant females divided by trimesters, compared to matched control. METHODOLOGY: We recruited 89 normal pregnant females and 30 age matched controls. Five minutes resting HRV was measured by Variowin HR, software-based instrument, by standard protocols to yield time-domain, frequency domain, and Poincare plot parameters. They were further compared between groups for difference. RESULTS: Case groups (three based on trimesters) and control group were comparable. There was reduced HRV in case than control group, with statistical significance for all, more for frequency domain than time-domain or Poincare plot parameters. There was no pattern of HRV trend across three trimesters, but mostly second trimester was associated with major decline. Primipara revealed significantly reduced HRV than multipara, but anemia or working status was not significantly associated with HRV in case group. CONCLUSION: There is global HRV reduction in normal pregnancy across all trimesters, associated with primiparity. This indicates pregnancy as a significant risk with reference to altered cardiac balance and use of HRV as a good tool to assess the same.