Spot heart defects early to increase survival. (Routine Surveillance Inadequate).

CANCUN, MEXICO -- Prenatal detection of congenital heart defects can improve an infant's chance of survival if delivery is then done at a tertiary cardiac center.

But most congenital heart defects won't be seen with a prenatal ultrasound examination unless the fetus is at high risk and comprehensive examinations are done, Dr. Joshua A. Copel said at a conference on obstetrics, gynecology, perinatal medicine, neonatology, and the law.

In the Routine Antenatal Diagnostic Imaging With Ultrasound Study (RADIUS), which during the early 1990s assessed the efficacy of two routine, prenatal ultrasound examinations in low-risk fetuses, the detection rate for congenital heart defects was 0% when examinations were done by primary care physicians, but 23% when the ultrasound examinations were done at tertiary referral practices.

"The standard of care is that routine ultrasound cannot detect most cases of congenital heart disease; even in tertiary practices, only [about] 25% of defects were seen," said Dr. Copel, director of obstetrics at Yale-New Haven Hospital.

On the flip side, the positive predictive value of a putative heart defect seen with ultrasound is about 50%.

The deficiencies of ultrasound for prenatal diagnosis are a problem, because congenital heart defects are not rare but they are very dangerous.

The defects have a prevalence of about 8 in every 1,000 live births. An average obstetrician who delivers about 10 infants a month will deliver one baby with a congenital heart defect about every 20 months. In the United States, congenital anomalies are the No. 1 killer of infants up to 1 year old, causing about 21% of all deaths in this group; about a third of these congenital anomalies involve congenital heart disease.