Abstract
Few studies have addressed the prenatal detection rate of congenital heart defects in a non‐selected population at 18 weeks of gestation. Our objective was to assess the change in the prenatal detection rate of congenital heart defects in such a population that resulted from incorporating the four‐chamber view at the second‐ trimester routine ultrasound examination. The prenatal detection rate of heart defects was prospectively compared between 4435 fetuses in Phase I who were stunned without special attention to the heart, and 7459 fetuses in Phase II who were scanned incorporating the four‐chamber view. Of the 49 heart defects in Phase I, 17 (35%) were critical and three (18%) of these were detected prenatally. Of the 90 heart defects in Phase II, 23 (26%) were critical, six (26%) of these were detected prenatally at the 18 weeks' routine stun, and three were detected in the third trimester, providing a total prenatal detection rate of 39%. A defect was classified as critical when a surgical repair was likely to be required because of gross structural complexity having a functional significance, e.g. transposition of the great arteries, hypo‐plastic left heart syndrome, atrioventricular septal defect, coarctation of the aorta, and large ventricular septal defect. No non‐critical heart defects were detected prenatally in either of the phases. The incidences in the total population were 11 and 12/1000 in Phases I and II, respectively. Thirty‐two per cent of the critical and 16% of the non‐critical defects had associated abnormalities and/or abnormal karyotype. Implementation of the four‐chamber view increased the prenatal detection rate of critical heart defects. To improve the results significantly, education and an extended fetal heart examination are necessary. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology