A comparison of heart rate variability in women at the third trimester of pregnancy and during low-risk labour.

Abstract Heart rate variability (HRV) has been recognised as a non-invasive method for assessing cardiac autonomic regulation. Aiming to characterize HRV changes at labour in women, we studied 10 minute ECG recordings from young mothers ( n  = 30) at the third trimester of pregnancy (P) or during augmentation of labour (L) ( n  = 30). Data of the L group were collected when no-contractions (L-NC) or the contractile activity (L-C) was manifested. Accordingly, the inter-beat interval (IBI) time series were processed to estimate relevant parameters of HRV such as the mean IBI ( IBI ¯ ), the mean heart rate HR ¯ , the root mean square of successive differences ( RMSSD ) in IBIs, the natural logarithm of high-frequency component ( LnHF ), the short-term scaling parameters from detrended fluctuation and magnitude and sign analyses such as ( α 1 , α 1(MAG) , α 1(SIGN) ), and the sample entropy ( SampEn ). We found statistical differences ( p RMSSD among P and L-NC/L-C groups (25 ± 13 vs. 36 ± 14/34 ± 16 ms) and for LnHF between P and L-NC (5.37 ± 1.15 vs. 6.05 ± 0.86 ms 2 ). Likewise, we identified statistical differences ( p α 1(SIGN ) among P and L-NC/L-C groups (0.19 ± 0.20 vs. 0.32 ± 0.17/0.39 ± 0.13). By contrast, L-NC and L-C groups showed statistical differences ( p α 1(MAG) (0.67 ± 0.12 vs. 0.79 ± 0.12), and SampEn (1.62 ± 0.26 vs. 1.20 ± 0.44). These results suggest that during labour, despite preserving a concomitant non-linear influence, the maternal short-term cardiac autonomic regulation becomes weakly anticorrelated (as indicated by α 1(SIGN) ); furthermore, an increased vagally mediated activity is observed (as indicated by RMSSD and LnHF ), which may reflect a cholinergic pathway activation owing to the use of oxytocin or the anti-inflammatory cholinergic response triggered during labour.