Congenital heart defects: natural course and in utero development.

Background: Most congenital heart defects (CHDs) are diagnosed on targeted prenatal transvaginal (TVS) or transabdominal (TAS) ultrasonography during the early second trimester or at midgestation. Nevertheless, delayed diagnosis in some cardiac malformations still remains despite detailed echocardiographic examination. The present study was conducted to evaluate the evolution of fetal cardiac anomalies and assess their development in utero.
Methods and Results: We retrospectively reviewed 22,050 pregnant women who were divided into two groups: 6924 who had initial TVSs at 13 to 16 weeks' gestation, followed by TASs at 20 to 22 weeks, and 15,126 who had initial TASs at 20 to 22 weeks. Both groups were subsequently examined in their third trimester. All newborns were examined by certified pediatricians. CHD was diagnosed in 168 babies: 66 in group A and 102 in group B. In group A, 42 malformations (64%) were detected at the first TVS examination, and 11 (17%) were found during the subsequent TAS. Three additional anomalies (4%) were found during the third trimester, and 10 malformations (15%) were detected postnatally. In group B, 80 malformations (78%) were detected in the initial examination at midtrimester, and an additional 7 (7%) were found in the third trimester, whereas 15 (15%) were diagnosed postnatally. The 10 anomalies (group A, n=3; group B, n=7) that were detected only during the third trimester comprised aortic stenosis (n=2), cardiac rhabdomyoma (n=2), subaortic stenosis (n=1), tetralogy of Fallot (n= 1), aortic coarctation (n=1), sealed foramen ovale (n=1), ventricular septal defects (n=1), and hypertrophic cardiomyopathy (n=1).
Conclusions: Although most fetal cardiac anomalies are detectable early in gestation, some may evolve in utero at different stages of pregnancy.