Abstract
Maternal and fetal heartbeat couplings are evident throughout fetal development. Most of the published work, however, did not consider maternal physiological factors such as Heart Rate Variability (HRV), and did not investigate the interrelationships of maternal-fetal coupling parameters. The aims of this study are to investigate whether: 1) maternal-fetal Heart Rate (HR) coupling ( $\lambda $ -based) parameters are associated with fetal development, and 2) fetal gold standard Gestational Age (GA) can be estimated using maternal-fetal HR coupling and variability of various recording lengths. The study considered Electrocardiogram (ECG) signals from 60 healthy pregnant women with no records of fetal abnormalities. HRV and $\lambda $ parameters at various Maternal:Fetal coupling ratios were calculated, and stepwise regression was utilized to create generalized linear regression models considering various lengths of recorded signals (1 and 5 min) to produce a robust estimate of fetal age. Cross-validation performances were evaluated by the mean square root of the average of squared errors (mRMSE) between age values estimated by the proposed models and gold standard GA identified by Crown-Rump Length (CRL). Effect of Fetal Behavioral States (FBSes) on proposed models with different recording lengths was considered to examine the highly nonstationary nature of signals. We found that HR coupling strength for a specific ratio is not constant throughout gestation. Results showed that ratios of 2:3 and 2:4 were common between the proposed models. The value of $\lambda $ [2:3] was found to be positively correlated with GA, while $\lambda $ [2:4] had a negative correlation. Compared with gold standard GA identified by CRL, the proposed regression model resulted in mRMSE of 2.67 and 3.69 weeks for the recordings of 5 and 1 min, respectively. However, when FBS was considered, both models produced lower estimation errors. Fetal GA can be more reliably estimated by a multivariate model incorporating fetal and maternal HR coupling and HRV parameters using 5 min of ECG signals.
Highlights
The American College of Obstetricians and Gynecologists provided guidelines for estimating the due date based on ultrasonography and the Last Menstrual Period (LMP) in pregnancy [1]
One of the main challenges when confirming Gestational Age (GA) using Crown-Rump Length (CRL)-based methods or standard ultrasonography techniques in general is being subject to human errors and requiring good clinical practice administered by highly-skilled technicians [8], which might not be feasible in low- and middle-income settings
In our preliminary study [20], we showed that it is possible to estimate the GA by using maternal-fetal Heart Rate (HR) coupling strengths with fetal and maternal Heart Rate Variability (HRV) parameters using ECG signals recorded for 10 min
Summary
The American College of Obstetricians and Gynecologists provided guidelines for estimating the due date based on ultrasonography and the Last Menstrual Period (LMP) in pregnancy [1]. Up to the first trimester of pregnancy, ultrasound measurement of the embryo is considered to be the most accurate method to confirm Gestational Age (GA) [2], [3]. Measurements of the Crown-Rump Length (CRL) of the fetus earlier in the first trimester of pregnancy are more accurate [4], [5] with an error of ±5–7 days [6], [7]. One of the main challenges when confirming GA using CRL-based methods or standard ultrasonography techniques in general is being subject to human errors and requiring good clinical practice administered by highly-skilled technicians [8], which might not be feasible in low- and middle-income settings. A more robust approach is required to estimate the GA
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