Cardiac time intervals of normal fetuses using noninvasive fetal electrocardiography

Objectives To evaluate the fetal cardiac time intervals from the longitudinal analysis of noninvasive fetal electrocardiography (fECG) in normal pregnancies. Methods One hundred singleton pregnancies were examined in this longitudinal study. Cardiac time intervals were derived from fetal electrocardiograms obtained noninvasively using three electrodes placed on the maternal abdomen. The variables measured included the durations of the P wave, PR interval, QRS complex, QT interval and T wave. Results Success rates for detecting the P, QRS and T waves were 74.6, 91.0 and 79.3%, respectively. Cardiac time intervals were significantly influenced by fetal age. The mean P-wave duration increased from 43.9 (18-22 weeks) to 52.9 ins (>= 37 weeks) (p < 0.001). PR intervals were 102.1 and 110.1 ms, for fetuses at 18 to 22 and >= 37 weeks (p < 0.001), respectively. QRS intervals were 47.2 and 52.6 ms (p < 0.001), while QT intervals were 224.0 and 242.7 ms (p < 0.001), at 18 to 22 and > 37 weeks respectively. From 18 to 22 weeks to > 37 weeks, QT, values increased from 343.8 to 367.7 ms (p < 0.001), while T-wave durations increased from 123.8 to 152.4 ins (p < 0.001). Conclusions Serial noninvasive fECG of normal fetuses from 18 to 41 weeks of gestation show good success rates of fECG detection. Cardiac time intervals generally increased with increasing gestational age. Copyright (c) 2005 John Wiley & Sons, Ltd.