To assess foetal electrocardiographic intervals across gestational age among foetuses with and without congenital heart disease, and to investigate differences between groups.

A prospective observational cohort study.

Center for Prenatal Pediatrics, Morgan Stanley Children’s Hospital of NewYork-Presbyterian.

A total of 92 participants with singleton pregnancies, 41 with normal anatomy and 51 with congenital heart disease were included in this study.

Using a maternal abdominal monitor, foetal electrocardiogram was obtained serially from foetuses with and without congenital heart disease at 20–24 weeks (F1), 28–32 weeks (F2), and 34–38 weeks (F3) of gestation. A signal-averaged waveform was calculated, and PR, QRS, and QT intervals were measured. Intervals from controls were compared with gestational age norms. Using Pearson’s correlation coefficient, we analysed the relationship between gestational age and foetal electrocardiographic intervals. Intervals from control and congenital heart disease foetuses were compared by Student’s t-test.

PR (r=0.333, p=0.02) and QRS (r=0.248, p=0.05) intervals correlated with gestational age only among controls. QRS intervals in foetuses with congenital heart disease were significantly longer than controls at F1 (63±6 versus 52±5 ms, p<0.001), F2 (61±8 versus 56±7 ms, p=0.02), and F3 (64±10 versus 56±9 ms, p=0.007).

PR and QRS intervals lengthen across gestational age among foetuses with normal cardiac anatomy but not in foetuses with congenital heart diseases. As early as 20 weeks of gestation, differences between foetuses with and without congenital heart disease are discernible, with congenital heart disease foetuses demonstrating longer QRS intervals compared with controls.