AimsTo evaluate cardiac findings in newborn twins from the general population and investigate if newborn twins may require systematic evaluation of cardiac parameters.MethodsProspective cohort study of newborns with cardiac evaluation performed during the first month of life. Cardiac findings were compared 1:3 with matched singletons.ResultsWe included 412 newborn twins (16% monochorionic; 50% boys) and 1236 singletons. Comparing cardiac findings showed twins had an increased prevalence of non‐severe structural heart disease (most common: ventricular septal defects in both groups), thinner left ventricular posterior wall in diastole (LVPWd; 1.82 vs. 1.87 mm, p = 0.02), smaller diameter of the left atrium (10.6 vs. 11.1 mm, p = 0.04), higher heart rate (148 vs. 144 bpm, p = 0.04), more left‐shifted QRS axis (106 vs. 111°, p < 0.001), and lower maximum R‐wave amplitude in V1 (927 vs. 1015 μV, p = 0.02) compared to singletons. After multifactorial adjustment for potential confounders, the effect of twinning on cardiac parameters persisted only for LVPWd (p < 0.05).ConclusionDespite contemporary surveillance, we found an increased prevalence of non‐severe structural heart disease in a population‐based cohort of newborn twins. However, the effect of twinning on cardiac parameters was modest and generally did not persist after correction for likely confounding factors.

Background Myocardial development is still incomplete by the time of birth making the cardiomyocyte vulnerable in the perinatal period. However, little is known on whether perinatal factors affect the neonatal electrocardiogram, and if so, to what degree these effects persist in the neonatal period. Purpose To investigate the impact of maternal and perinatal factors on the neonatal electrocardiogram in a large unselected cohort of neonates. Methods In a multicentre, prospective, population-based cohort study, neonates underwent cardiac evaluation during the first month of life. Electrocardiograms and echocardiograms were obtained and systematically analysed. Medical and demographic information on the parents, pregnancy, and birth-related factors were registered, and the following perinatal risk factors were evaluated: maternal comorbidities, maternal BMI ≥25, use of assisted reproduction technology, parity, (preterm) premature rupture of membranes, placental disorders, abnormal foetus presentation, induction of labour with synthetic hormone, instrumental induction, administration of nitrous oxide, epidural/spinal administration, labour ≥24h, pushing stage ≥1h, Caesarean section, and instrumental delivery. Results A total of 15,928 singletons with normal echocardiograms were included (52% boys; median age at examination 11 days). The neonates were divided into groups by accumulated number of perinatal risk factors: 0 (n=1,587), 1 (n=3,718), 2 (n=4,026), 3–4 (n=4,998), and ≥5 (n=1,197), and differences in ECG parameters between the groups were analysed. Heart rate, QRS axis, uncorrected QT interval, QTcBazett, QTcFridericia, and maximum amplitudes in R-V1 and R-V6 differed across the five subgroups (all p&lt;0.05). We observed a cumulative effect of perinatal risk factors on ECG parameters with increasing left-shift in the QRS axis, prolongation of the QT interval, and increasing amplitudes in R-V1 and R-V6. The subgroup with ≥5 perinatal risk factors differed the most, and absolute differences between this subgroup and neonates without any perinatal risk factors were 7.6% in maximum amplitudes in R-V6 (940 vs. 874 μV, p&lt;0.01), 4.3% in R-V1 (1,201 vs. 1,152 μV, p&lt;0.05), 5.1% in the QRS axis (111 vs 117°, p&lt;0.0001) and 0.8% in QTcFridericia (366 vs. 363 ms, p&lt;0.01). Conclusion We observed a cumulative effect of perinatal risk factors including a significantly more left-shifted QRS axis, increased values of the QT interval, and higher amplitudes in R-V1 and R-V6 in the subgroup with ≥5 perinatal risk factors. These findings suggest a relatively lower right ventricular dominance pattern, discrete prolongation of the QT interval and increased myocardial mass of the right ventricle in neonates exposed to multiple perinatal risk factors. However, the absolute differences in ECG parameters were relatively small. These findings may be useful for identification of neonates with increased cardiovascular risk. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Department of Cardiology, Herlev-Gentofte Hospital, Internal Funding