We are developing a non-invasive, transabdominal fetal oximeter, to provide worried mothers and obstetricians needed information regarding fetal well-being, namely fetal oxygenation, to reduce the number of unnecessary emergency C-sections. This is done by transmitting light in the near-infrared spectrum through the maternal abdomen and fetus to measure the oxygen saturation in the fetal blood using pulse oximetry. Pulse oximetry is a technique that utilizes the light absorption spectra of oxy- and deoxy- hemoglobin and captures a photoplethysmograph (PPG) from the vascular pulsations of the cardiac cycle. This PPG signal can then be used to calculate the oxygen saturation of the blood based on how much light was detected per heartbeat. In our case, a mixed maternal-fetal PPG is captured since light is traversing both maternal and fetal tissue, to which the fetal contribution can be isolated through Fourier analysis and filtering.
Cesarean section (C-section) is a major abdominal surgery which introduces significant risks to the mother and can have long-term effects on the respiratory health of the fetus . While the World Health Organization has identified that an ideal C-section rate is between 10-15% to not be under- or overused, many countries report having rates much higher . In 2014, the United States had an unacceptably high-rate of 32.2% . This is in part due to the current paradigm used for monitoring fetal well-being.
Electronic fetal heart rate monitoring (EFM) was adopted in the 1970’s as a means of assessing fetal well-being during labor and delivery and decrease the incidence of cerebral palsy and neonatal death. However, the rates of cerebral palsy, neonatal death, low Apgar scores, and perinatal death remained unchanged with its introduction, while the rate of C-sections rose dramatically . Despite the overwhelming evidence that EFM has not decreased adverse health outcomes, a high-proportion of C-sections are performed partly or fully in response to a non-reassuring EFM trace . Current interpretations of such traces is that it is suggestive of inadequate blood flow to the fetal brain and, if left untreated, can lead to cerebral palsy, fetal acidosis, and other harmful conditions. However, studies have shown that interpretations of EFM traces are unreliable, produce a high rate of false-positives (99.8%), and may be related to a normal chemoreflex response of the fetus .
Clearly there is a need for new fetal well-being monitoring techniques. To address this issue and reduce the number of unnecessary emergency C-sections performed, we have developed a device that will non-invasively give physicians information on fetal oxygenation in utero, previously unattainable during critical stages of labor and delivery.
Daniel D. Fong, André Knoesen, Mohammad Motamedi, Terry O’Neill, and Soheil Ghiasi. “Recovering the Fetal Signal in Transabdominal Fetal Pulse Oximetry“, Smart Health, Volumes 9–10, December 2018, Pages 23-36.
Daniel Fong, André Knoesen, Soheil Ghiasi. “Transabdominal Fetal Pulse Oximetry: The Case of Fetal Signal Optimization“, IEEE 19th International Conference on e-Health Networking, Applications and Services (HealthCom), October 2017.
This work was gratefully supported by a seed grant from CITRIS and the Banatao Institute at the University of California.
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