Wakai pioneers fetal magnetocardiography and magnetoencephalography, developing SERF-OPM and SQUID biomagnetometry to record fetal and neonatal heart and brain signals for clinical assessment. This vapour-phase approach reaches femto-to-picotesla sensitivities complementary to NV-center diamond ensemble quantum sensors (DEER, nano-NMR, T1 relaxometry) that operate near the pT/sqrt(Hz) regime.