Design and Validation of a Signal Processing Algorithm for Fetal Heart Rate Monitoring from Abdominal ECG in Nigerian Antenatal Settings

Non-invasive fetal heart rate monitoring through abdominal ECG provides higher fidelity cardiotocographic data than conventional Doppler ultrasound CTG, but the signal processing challenge of extracting the fetal ECG from a composite maternal-fetal abdominal signal in conditions representative of Nigerian antenatal clinic settings has not been addressed by existing algorithms validated in high-income country environments. This study designs and validates a signal processing algorithm for fetal heart rate extraction from abdominal ECG recordings acquired under Nigerian antenatal clinic conditions, addressing the specific noise and signal quality characteristics of the Nigerian clinical context. Abdominal ECG signals were collected from forty-five pregnant women in the third trimester at the Lagos University Teaching Hospital using a custom-designed four-electrode abdominal ECG acquisition system. Reference fetal heart rate was provided by simultaneous scalp electrode fetal ECG recording. Signal processing algorithms tested include adaptive maternal ECG cancellation using recursive least squares adaptation, independent component analysis, and a novel empirical mode decomposition-based approach developed specifically for the higher motion artifact levels characteristic of awake ambulatory patients in Nigerian clinic environments. Algorithm performance was evaluated by comparing fetal heart rate estimates against scalp ECG reference values across the full recording dataset. The empirical mode decomposition approach achieved mean fetal heart rate estimation error of 2.1 beats per minute and fetal QRS detection sensitivity of 93.7 percent, outperforming the adaptive cancellation and ICA approaches under high motion artifact conditions typical of the clinical setting. The study provides a validated algorithm ready for embedded implementation in a low-cost Nigerian fetal monitoring device. Keywords: fetal heart rate monitoring, abdominal ECG, signal processing, antenatal care, Lagos.