Roger K. Freeman, Thomas J. Garite, Michael P. Nageotte, Fetal Heart Rate Monitoring Third Edition, 2003, p. 3. "The earliest preliminary report of FHR monitoring came in 1958 from Edward Hon, MD,... via fetal ECG monitor on the maternal abdomen."
Google Books citation
Church, Charles (April 2007). "Quantification of risk from fetal exposure to diagnostic ultrasound". Progress in Biophysics and Molecular Biology. 93 (1–3): 331–353. doi:10.1016/j.pbiomolbio.2006.07.015. PMID16949653.
Church, Charles (April 2007). "Quantification of risk from fetal exposure to diagnostic ultrasound". Progress in Biophysics and Molecular Biology. 93 (1–3): 331–353. doi:10.1016/j.pbiomolbio.2006.07.015. PMID16949653.