Mid-trimester maternal heart rate is related to neonatal birth weight

Objective(s): We sought to establish the relationship between maternal mid-trimester heart rate (HR) and neonatal birth weight in women at high a priori risk of preeclampsia. Study Design: Ninety-nine women were recruited following second trimester uterine artery Doppler assessment. Maternal blood pressure (BP) and HR were measured between 23⁺⁴ and 30⁺⁵ weeks gestation and neonatal birth weight was expressed as a z-score. The relationship between the parameters was investigated using Pearson's correlation coefficient. Results: There was a significant positive correlation between maternal HR and neonatal birth weight z-score, r=0.22 (95% CI: 0.02-0.40), p=0.03. An inverse correlation was found between uterine artery Doppler pulsatility index (PI) and maternal HR, r=-0.43 (95% CI: 0.01-0.40), p=0.0001, and neonatal birth weight, r=-0.3 (95% CI:-0.47 to-0.10), p=0.004. For neonatal birth weight z-score <-1.65, r=0.69 (95% CI: 0.15-0.91), p=0.02. There was no relationship between BP and uterine artery Doppler or neonatal birth weight. Conclusion: The finding of a continuous relationship between maternal HR and neonatal birth weight prior to the onset of fetal growth restriction is novel, suggesting that maternal cardiovascular adaptation is reflected by neonatal birth weight. Lower maternal HR is associated with lower neonatal birth weight and vice versa. Further, we confirm the reported associations between uterine artery Doppler PI and both maternal HR and neonatal birth weight.