Matthiesen NB, Østergaard JR, Hjortdal VE, et al. - In this nationwide, registry-based study, researchers sought to estimate the correlation between major types of congenital heart defects (CHD) and spontaneous preterm birth, and to evaluate the potential underlying mechanisms. For this analysis, they involved a cohort of all singleton pregnancies in Denmark from 1997 to 2013. The link between CHD and spontaneous PTB was estimated by multiple Cox regression, adjusted for potential confounders. The study involved 1,040,474 births. CHD, particularly right ventricular outflow tract obstruction, were linked to an increased risk of spontaneous PTB. The risk was carried by CHD rather than maternal genetics. In addition, as a potential underlying mechanism, preterm prelabor rupture of membranes was identified.