Introduction Patency of the oval foramen (PFO) and atrial septal defects (ASDs), i.e. interatrial communications, have been reported to be present in 24–92% of newborns. For isolated ASDs, the reported prevalence varies from 0.3–2.4 per 1000 livebirths. This broad range partly reflects the absence of a clear and universal clinical classification of interatrial communications. On this basis we have recently proposed a clinically applicable echocardiographic algorithm for classification of interatrial communications (figure 1), which proved superior to standard assessment by experts in terms of inter- and intraobserver agreement. Purpose To determine the prevalence of interatrial communications in newborns. Methods Echocardiograms (TTEs) from newborns (0–30 days) included in a population study (N>25,000) were assessed/analyzed for interatrial communications according to the new algorithm and categorized into three PFO subtypes and three ASD subtypes. Results TTEs from 16,420 newborns were analyzed; 3,694 (22.5%) were excluded due to suboptimal image quality and 9 (<0.1%) were excluded due to concurrent severe congenital heart disease. Of the remaining 12,718 included newborns (median age 12 days [8; 15], 48.1% female), an interatrial communication was present in 10,033 (78.9%) cases; 9,274 (72.9%) cases were classified as PFO while 759 (6.0%) were classified as ASD. In the ASD group, 368 (48.5%) had a defect size ≥4 mm, 364 (48.0%) had multiple interatrial communications, and 27 (3.6%) had the defect located in the lower 1/3 part of the septum (figure 2). Conclusion An interatrial communication was present in almost 4 out of 5 newborns. ASD was diagnosed in 6% of the newborns and the prevalence of PFO was 12 times higher than the prevalence of ASD. Follow-up studies of these children are expected to provide clinically useful information on the long term structural and hemodynamic impact of these well categorized ASD and PFO subtypes. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Candy's Foundation, The Danish Children's Heart Foundation

Background and introduction Maternal pre-existing and gestational diabetes affect approximately 6% of all pregnancies in Denmark and are well known risk factors for congenital heart disease (CHD). Worldwide, CHD is the most common congenital defect and a leading cause of infant death. The association between maternal diabetes, and CHD in the offspring has previously been studied, however, these studies have been limited by small study cohorts and/or registry studies without systematic transthoracic echocardiography (TTE) of the children. Purpose To assess the prevalence of atrial and ventricular septal defects (ASD and VSD) in children born to mothers with pre-existing or gestational diabetes by systematic TTE, in a large, population-based cohort of neonates. Method Systematic, standardized TTE was performed in neonates included in a population-based cohort study between 2016 and 2018. For the present study, the prevalence of VSD in cases and controls was assessed in the entire cohort of neonates who underwent TTE within 30 days of birth, and in whom information regarding maternal diabetes was available (n=24,921). The prevalence of ASD was assessed in a sub-cohort of neonates (n=12,682) with the same inclusion criteria and in whom an interatrial communication had been classified as ASD or patent oval foramen according to a validated algorithm. ASD was defined as an interatrial communication with a defect size ≥4mm, a location in the inferior 1/3 of septum, or multiple communications. VSD was defined as flow across the interventricular septum in colour Doppler mode in one or more views. VSDs were classified as either muscular, perimembranous, or subarterial. Information about maternal pre-existing and gestational diabetes was collected from review of the mother's medical records and from an Obstetrical Database maintained by the participating hospitals. Cases were compared with controls, which here consists of the full cohort for VSD and sub-cohort for ASD, respectively, after excluding cases. Results The median age at examination of the entire cohort was 11 days [interquartile range (IQR) 7; 14] and 48% were female. The prevalence of VSD in children with maternal diabetes was 3.1% compared with 3.3% among children of mothers without maternal diabetes, RR 1.00 (95% CI 0.99–1.01, p=0.771). There was no difference between cases and controls when comparing the prevalence of subtypes of VSD (table 1). In the sub-cohort of 12,682 neonates assessed for ASD (median age at examination 12 days [IQR, 8; 15], 48% female), the presence of an ASD was found in 7.3% of cases compared to 5.9% among controls, RR 0.81 (95% CI 0.59–1.13, p=0.214). Conclusion In a large population-based cohort of infants, we did not find an increased risk for ASD or VSD, nor any of the subtypes of VSD, among children born to mothers with pre-existing or gestational diabetes as compared to controls. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): The Capital Region of Denmarks Research Fund.The Research Council of Herlev and Gentofte Hospital.