631: Noninvasive fetal heart rate monitoring: Abdominal fetal ECG v. Doppler ultrasound cardiotocogram in obese patients


      Noninvasive fetal echocardiography (fECG) is a unique method of fetal heart rate (FHR) monitoring. We aim to investigate the clinical utility of a novel noninvasive abdominal fECG device as compared to the standard of care Doppler ultrasound cardiotocography (CTG) in obese patients.

      Study Design

      We conducted a prospective observational study of women from December 2018 to July 2019. Inclusion criteria: maternal BMI > 30 kg/m2, nonanomalous, singleton gestation. Patients were monitored simultaneously with the noninvasive fECG and CTG device for thirty minutes. Two blinded obstetricians independently analyzed the tracings. The primary outcome: average number of uninterpretable minutes of tracing of the fECG device as compared to CTG. Secondary outcomes included a comparison of baseline FHR, variability, number and onset of FHR accelerations and decelerations. The generalized estimating equation normal and Poisson models with identity and log links were used to calculate outcomes. Kappa indices between the two observers were computed for each outcome.


      55 patients were recruited. Nine patients were excluded from analysis due to technical error of the fECG device and poor signal quality. Monitoring with the devices simultaneously yielded a total of 1303.66 minutes of tracing. On average, the fECG device had 2.71 minutes more of uninterpretable tracing (effect estimate 2.71, (0.45, 4.98), p=0.02) as compared to CTG. Overall, the fECG device was no different in its ability to detect baseline FHR (effect size 0.1 (-1.00, 1.20) p=0.86), variability, and number of FHR accelerations/decelerations (effect size 0.87 (0.69, 1.1) p=0.25). A Kappa agreement index for the timing of onset of accelerations/decelerations was calculated to be 0.18 (-0.23, 0.59).


      Noninvasive fECG yielded on average 2.71 minutes more of uninterpretable tracing out of 30 min compared to the CTG device. In all other parameters of FHR tracing it performed similarly. Given that the noninvasive fECG device is wireless and therefore allows ambulation, consideration should be given to its use as an alternative to Doppler CTG.
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