Poor prenatal detection rate of cardiac anomalies in Noonan syndrome.

Background: The wide variation and nonspecific nature of many of the associated ultrasonographic findings complicate prenatal diagnosis of Noonan syndrome. The aim of the present study was to define the rate of prenatal diagnosis of heart malformations in cases diagnosed postnatally with Noonan syndrome.

Methods: English-language literature review of 29 cases of Noonan syndrome examined prenatally with confirmed postnatal diagnosis and four case reports from our center.

Results: Cases were evaluated for cervical spine pathologies, cardiac anomalies and other pathological findings, including hydrops fetalis and polyhydramnios. Cardiac anomalies were suspected in only nine of 33 cases; three of these were associated with cystic hygroma. Cardiac anomalies were eventually diagnosed in 31/33 cases postnatally. Polyhydramnios was diagnosed in 19/33 cases in the third trimester, and hydrops fetalis was detected in eight of 33. Cystic hygroma was present in a total of nine cases at mid-trimester.

Conclusions: Noonan syndrome is characterized by late-onset and progressive pathologies, particularly the associated cardiac anomalies, which develop through the course of gestation and postnatal life. This complicates or precludes prenatal diagnosis at mid-trimester or at any time in the prenatal period, and partly explains the low rate of detection of fetal cardiac lesions in this syndrome.