Prenatal Manifestations of the RASopathies

The RASopathies are a cohort of common congenital anomaly syndromes that have unique fetal features, which can be detected on routine prenatal ultrasounds. These features may develop at any point in gestation, ranging from the first to third trimester. Examples of such features include lymphatic abnormalities and fetal effusions, congenital cardiac defects, macrocephaly, macrosomia, renal abnormalities, and others. Some disease-specific features are also beginning to be understood, such as an increased prevalence of fetal arrhythmias among cases of Costello syndrome. Earlier and more accurate diagnosis of fetal RASopathies is essential for improved management of affected pregnancies, counseling about prognosis, and anticipation of neonatal needs. Moving forward, larger studies with long-term follow-up are needed to correlate postnatal outcomes with prenatal findings by specific disease as well as genotype.