The CBHS is a large population study examining the hearts of newborn babies. From April 1, 2016 to October 31, 2018, all expectant parents at three large hospitals in the Copenhagen capital region of Denmark were invited to participate in the study, offering a comprehensive cardiac examination of their child, preferably within the first 14 days after birth. The CBHS also gathered information regarding the parents’ health and socioeconomic status. Furthermore, the study collected information about the pregnancy and birth as well as an umbilical cord blood sample, which is stored in a biorepository. Of the children born, 51.5% were male, and 49.5% were female.