Prenatal detection of univentricular heart and transposition of the great arteries in Finland

A congenital heart defect (CHD) is the most common congenital structural anomaly, and it is observed in 1% of live births. In Finland, approximately 550 children per year are born with a CHD. The defect is critical in 10%, requiring immediate care soon after birth. Due to developed care, most CHD patients survive adulthood, but a critical CHD is still one of the most important reasons for perinatal mortality. Information on CHD risk factors is still scarce. By uniting data from quality, nationwide registers, this study assessed the total and live birth prevalence of the selected CHDs and the effect of the implementation of national fetal anomaly screening on prenatal detection rates nationally and regionally in an 11-year cohort. In addition, the monthly variation of these CHDs was analyzed, and possible analogous variations n in viral or bacterial infections were evaluated. Prenatal anomaly and chromosomal screenings have become a pivotal part of health care. In Finland, voluntary, nationwide, free-of-charge ultrasound screenings have been provided by the municipalities for every pregnant woman since January 2010. Fetal heart screening is based on a four-chamber view and outflow tract views. This study selected the univentricular heart (UVH, in which one ventricle is taking care of circulation) as an index anomaly for the four-chamber view and transposition of the great arteries (a TGA, in which the aorta arises from the right ventricle and the pulmonary trunk from the left ventricle) for the outflow tract views. The data of all live births, stillbirths and terminated pregnancies, and maternal characteristics were gathered with ICD codes in 2004–2014. The cases with a congenital diaphragmatic hernia and a CHD in 2002–2011 were collected for Study III. The population-based cohort included data from the National Institute for Health and Welfare’s; Finnish Register of Congenital Malformations, Medical Birth Register, The Register of Induced Abortions, Hospital Discharge Register, National Infectious Diseases Register, causes of death from Statistics Finland, and the National Register of Pediatric Cardiac Surgery maintained by Children’s Hospital at Helsinki University Hospital. Nationwide prenatal detection rates increased after implementing a systematic screening program: in UVH from 50% to 83% and in TGA from 12% to 41%. However, significant regional differences were found; especially in TGA, detection rates varied between 13% and 65% and remained still non-optimal. Significant monthly variation in early pregnancy was observed in a UVH and a TGA, but no analogous variation with studied bacterial and viral infections was found. Multiple pregnancies, obesity, and pregestational diabetes were more common among the CHD population than all parturients. None of the studied risk factors affected prenatal detection. Some extra-cardiac malformations, such as a congenital diaphragmatic hernia, were associated with the development of hypoplastic left heart syndrome (HLHS), warranting the close follow-up of heart development in fetuses with a diaphragmatic hernia. Neither the screening program nor the prenatal diagnosis affected simple TGA mortality. None of the prenatally diagnosed TGA infants died, and total mortality was 9%. Most of the deceased died in maternity hospitals without a prenatal diagnosis, and postoperative mortality was only 1%. Older maternal age and lower gestational age at birth were associated with higher mortality. Maternal prepregnancy obesity and perioperative risk factors were associated with a higher need for health care resources during the first year of life. In conclusion, the implementation of a systematic fetal screening program increased prenatal detection rates of UVH and TGA. However, for a TGA, there were significant regional differences, and the prenatal detection rates of TGA were still not optimal. These results suggest establishing the previously recommended prospective fetal screening register to assure equal, adequate, and quality screening nationwide.