Fetal heart rate and the neonatal QT interval: Results from a large general population study

Background Fetal bradycardia has been reported in neonates with congenital long QT syndrome, but it remains unknown whether there is a general association between fetal heart rate (FHR) and the neonatal QT interval. Objective We examined whether first- and second-trimester FHR measurements were associated with the neonatal QT interval. Methods We investigated neonates from a large population-based cohort study with available electrocardiograms (ECG) and first trimester FHR measurements (FHR1). We also investigated a subgroup with second-trimester FHR data (FHR2). The neonatal QTc interval was the primary outcome variable. Univariate and multiple regression analyses were also performed. Results The study cohort included 7,998 neonates (48.4% girls) with a median age of 11 days (interquartile range, IQR 7-14) at ECG recording. At a median gestation age (GA) of 90 days, we found a median FHR1 of 159 beats per minute (bpm; IQR 155-164) and no association with the QTc interval (adjusted difference 0.407×10 -4 ; 95%CI:-0.656×10 -4 to 0.147×10 -3 ; p>0.05 ) . The median FHR2 (available in 2,202 neonates; median GA 140 days) was 148 bpm (IQR 144–153), and lower FHR2 values were associated with longer QTc intervals (QTcFridericia 367 vs. 362 ms between outer quartiles). This association remained significant after multifactorial adjustment (adjusted difference -0.164×10 -3 ; 95%CI:-0.880×10 -4 to -0.110×10 -4 ; p