Non‐invasive fetal electrocardiography in singleton and multiple pregnancies

Abstract

Objectives To document the duration of fetal cardiac time intervals in uncomplicated singleton pregnancies using a novel non-invasive fetal electrocardiography (fECG) system and to demonstrate this technique's ability to acquire recordings in twin and triplet pregnancies. Design Prospective cross sectional observational study.Setting Antenatal wards and clinics, day assessment unit and centre for fetal care at a tertiary referral hospital, London, UK. Population or Sample Three hundred and four singleton and multiple pregnancies, 15-41 weeks of gestation.Methods Using electrodes sited on the maternal abdomen, a fetal electrocardiography (fECG) system was developed and tested on 304 pregnant women from 15 to 41 weeks of gestation, of whom 241 were uncomplicated singletons, 58 had twin and 5 had triplet pregnancies. The composite abdominal signals were stored on a laptop computer and the fECG derived off-line using a digital signal processing technique. For singletons, linear regression was used to analyse PR, QRS, QT and QTc intervals, and construct time-specific reference ranges. Main outcome measure Duration of fECG time intervals as a function of gestational age. Success of signal separation in singleton, twin and triplet pregnancies. Results For singletons, a total of 250 recordings was obtained from 241 individuals with a signal separation success rate of 85% (213/250). Success rates were significantly poorer between 27 and 36 weeks of gestation (2 Â k m 2 , P < 0.0001), with 84% (31/37) of separation failures occurring during this period. P, Q, R and S waves were seen in all cases where fetal signals were separated and were used to generate fECG time interval reference ranges. In 22% (43/199) of analysed cases, no T waves were identified, 63% (27/43) of whom were 24 weeks of gestation. In twins and triplets, separate fetal signals were obtained in 78% (91/ 116) and 93% (14/15), respectively; P, Q, R and S waves were evident in all averaged fECGs, while T waves were identified in 59% (54/91) and 57% (8/14). Conclusions This study provides reference ranges with gestation for fECG intervals derived non-invasively from normal singleton pregnancies and demonstrates the feasibility of obtaining complete fECG recordings non-invasively across a wide gestational range in pregnancies of all pluralities. The fECG time intervals described will enable the identification of pathological fECG recordings from high risk pregnancies where fECG abnormalities are suspected.

Fetal ECG: a novel predictor of atrioventricular block in anti-Ro positive pregnancies

“…A full fECG signature (including T waves) was obtained in 31 of the 35 (88.6%) separated signals. We have previously published reference ranges for fECG time intervals in a singleton cohort of 199 normal fetuses 15. A prolonged PR interval was defined as one lying above 95% gestational age-related confidence intervals (95% CI).…”

“…All mPR and ePR intervals measured in this study were plotted against published reference ranges (fig 1). 13 15 In most cases the mPR was longer than ePR because it includes electromechanical delay and isovolumic contraction time.…”

“…We have described the system and methodology fully elsewhere 15. The equipment used is portable and the size of a laptop computer.…”

“…The resulting sensitivity, specificity and positive and negative predictive value of both methods were compared. Z scores for ePR were calculated from 199 fetuses used to create our previous normal ranges15 and a receiver operator characteristic (ROC) curve was used to assess the area under the curve and to obtain threshold values. Sensitivity and specificity of the resulting diagnostic rule based on the Z score for ePR (zPR) is reported.…”

Extract Fetal ECG from Single-Lead Abdominal ECG by De-Shape Short Time Fourier Transform and Nonlocal Median

“…The twin pregnancy problem was relatively rarely discussed, except in Niknazar et al [17] and Taylor et al [65]. In Case 5 of the simulated database, although we do not specifically study in this paper, we mention that the proposed algorithm has the potential to handle even multiple pregnancy problem.…”