Electrocardiographic findings in newborns with inadequate intrauterine growth during pregnancy

Abstract Background Infants born small for gestational age (SGA) or following fetal growth restriction (FGR) have an increased risk of neonatal mortality as well as cardiovascular disease later in life. Prenatal electrocardiograms (ECGs) in fetuses with FGR exhibit QT prolongation. However, neonatal alterations in the conduction system in infants born SGA or with FGR has not previously been assessed in a large cohort of infants. Purpose To investigate potential variations in electrocardiographic parameters between infants born SGA or diagnosed with FGR, in comparison to infants born appropriate for gestational age (AGA). Methods This study was based on data from a population-based cohort study of infants (n>25,000) with prenatal inclusion and postnatal cardiac examination including eight-lead ECG between 2016-2018. We conducted a multiple linear regression analysis to compare ECG parameters among infants with FGR (birthweight <3rd percentile, n=544) and SGA (birthweight ≥3rd and <10th percentile, n=1,384) to infants born AGA (birthweight ≥10th percentile and <90th percentile, n=14,076). Parameters of interest included: heart rate (HR), uncorrected and corrected (Bazzet and Fridericia) QT intervals, QRS duration, PR interval, QRS axis, maximum amplitudes of the R- and S-waves in V1 and V6. All analyses were adjusted for infant sex, gestational age at birth, and weight, length, and age at ECG examination. Results Infants born SGA or with FGR had higher HR and consequently shorter uncorrected QT intervals compared with infants born AGA (Table 1). Infants with FGR had significantly shorter corrected (Fridericias) QT intervals. Infants born SGA had smaller amplitudes of both the R- and S-wave in V6, and significantly larger amplitude of the S-wave in V1, compared with infants born AGA (Table 1). Conclusion ECGs from infants born SGA and infants with FGR differed from infants born AGA, including higher HRs and shorter uncorrected QT-intervals even after adjustments for infant size and age at the examination. Furthermore, we saw infants born SGA had reduced amplitudes of the S and R wave in the lateral lead (V6), and an increased amplitude of the S-wave in V1, compared with infants born AGA. Follow-up examinations of these infants could determine whether these alterations persist beyond the neonatal period, and to fully understand their implications of the cardiac function later in life.