Making labor safer for women and their babies

Evaluation of the Fetal T/R Ratio Using a Fetal
Scalp Electrode and Abdominal Sensors

Caitlin McDonnell 1 ; Reza Sameni, PhD 2,3 ; Jay Ward 3 ; Jim Robertson 3
Adam Wolfberg, MD, MPH
3,4 ; Gari Clifford, PhD,1,3

1University of Oxford, 2Shiraz University, 3MindChild Medical, Inc.,
4Tufts Medical Center



The difference between the T/R ratio calculated from the scalp electrode and the T/R ratio calculated from the extracted abdominal fetal ECG was 0.0064 ± 0.014. This difference is not clinically meaningful.


We measured the fetal T/R ratio was accurately measured using abdominal electrodes in non-ischemic fetuses.





Fig. 1

Comparison of ECG waveform from

the FSE and abdominal sensors.

The T‐ and R‐waves are illustrated.


Fig. 2

Variation in T/R ratio between

FSE and abdominal sensors.




Evaluation of the T/R ratio - the
metric used by the STAN™
monitor - improves the accuracy of intra-partum fetal assessment when combined with fetal heart rate monitoring, but typically requires a fetal scalp electrode (FSE). Noninvasive measurement of the T/R ratio would make this metric more widely available.


To compare fetal T/R ratio measured using sensors on the maternal abdomen to the fetal T/R ratio acquired using a FSE.


Data were acquired from 27 term laboring women who had a FSE placed for a clinical indication. 31 channels of abdominal data were recorded simultaneously with the FSE.

The average T/R ratio level was estimated from 79 30-second segments from the FSE and the abdominal data for 4 subjects. A comparison was performed to assess the correlation between the fetal T/R ratio derived from abdominal sensors and T/R ratio measured using the FSE.




Disclosure: The authors, except for Ms. Pettigrew, hold equity in MindChild Medical, Inc., which has licensed intellectual property used to generate results presented in this abstract.








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