A real-time intrauterine catheter technique for fetal electrocardiogram monitoring

A fetal electrocardiogram (FECG) obtained via an intrauterine catheter (IC) is a compromise between the clinically accepted invasive scalp electrode, and the noninvasive abdominal wall approaches. The catheter is inserted into the uterus during delivery, but is non-invasive to the fetus. The IC can be modified to contain a pressure sensor to monitor contractions. The modified IC would enable fetal heart rate and contractions to be monitored with one sensor. Currently, two sensors that include the invasive scalp electrode and intrauterine pressure catheter are used clinically. Signal processing is required to obtain a FECG via the IC. Usually the maternal electrocardiogram (ECG) is present in the IC´s signal along with electromyographic noise. Obtaining the FECG in real-time further complicates the processing since the FECG can be similar in amplitude to the maternal ECG. Current techniques for maternal ECG cancellation produce a significant residual during the initial processing of the algorithm and/or falsely detect the FECG for the maternal ECG. A real-time IC technique is discussed. The results from clinical data from eight patients indicate a FECG with a good signal-to-noise ratio can be obtained even during the first seconds and minutes of operation.