Weight gain during pregnancy and its impact on maternal autonomic modulations and birth outcomes

Objectives: The study aimed to compare the heart rate variability (HRV) indices, a measure of cardiac autonomic modulation, and birth outcomes in mothers with below-adequate and adequate gestational weight gain. Materials and Methods: Eighty mothers (with low to normal body mass index [BMI]) were recruited in their first trimester. Fifty-one mothers were followed up throughout pregnancy. Maternal electrocardiogram (ECG) and anthropometry were collected at each trimester. Power spectral analysis was performed on ECG, and HRV indices were derived. Birth outcomes and anthropometric data were collected at birth. Participants were classified based on the Institute of Medicine (IOM) recommendations for weight gain into below adequate weight gain (BWG) group and adequate weight gain (AWG) group (cutoff of 12.5 kg for low BMI mothers and 11.5 kg for normal BMI mothers). Results: Mean weight gain during pregnancy was 9.6 ± 3.4 kg. Delta low frequency (LF), a marker of cardiac sympathetic activity (difference between the 1 st and 3 rd trimester), was lower ( P < 0.05) among the BWG group (−377.5 ± 686 ms 2 ) compared to the AWG group (−741.1 ± 581 ms 2 ). Spearman’s correlation demonstrated a positive association between delta LF and birth weight (r = 0.34, P < 0.05) in the BWG. Conclusion: Irrespective of BMI status, mothers gained lower weight than the (revised) IOM recommendations. BWG had decreased sympathetic modulations during pregnancy. Birth weight was positively correlated with greater sympathetic modulations even among women in BWG, thus highlighting the need to monitor autonomic modulations, along with weight gain during pregnancy effectively.