Maternal body mass index does not affect performance of fetal electrocardiography

The obesity epidemic challenges traditional antenatal fetal heart rate (FHR) monitoring technologies. Doppler signals in particular are attenuated. We sought to evaluate whether the performance of a novel transabdominal fetal electrocardiogram (fECG) device (AN24, Monica Healthcare) is influenced by body mass index (BMI). We performed a prospective observational study of singleton pregnancies (gestational age [GA] 20 to 41 weeks) monitored overnight with fECG. Recording quality ([RQ] %) of both the best hour and the total recording time of the FHR record were related to BMI. Two hundred four women were monitored. BMI ranged from 16.0 to 50.7 (median BMI 26.9). The correlation coefficient (with 95% confidence interval [CI]) between BMI and RQ was -0.35 (CI-0.60;-0.03) for the gestational age group 20⁺⁰ to 25⁺⁶ weeks, -0.08 (CI-0.28; 0.13) for GA 26⁺⁰ to 33⁺⁶ weeks, and -0.20 (CI-0.40; 0.03) for GA group ≥34⁺⁰ weeks. Median RQ in obese women (BMI ≥30 kg/m²) was 97.4, 98.9, and 100%, respectively. BMI has no clinically significant influence on recording quality of FHR monitored with fECG. It can therefore be considered a good method for monitoring the fetal condition in pregnancies of obese women.