Central nervous system anomalies.

The authors review the most common congenital anomalies of the central nervous system (CNS): neural tube defects (NTDs), ventriculomegaly/holoprosencephaly, hydranencephaly, holoprosencephaly sequence, iniencephaly, and microcephaly. They emphasize the importance of the diagnostic tools (biochemical markers of the maternal serum, ultrasound screening, invasive techniques), methods which are complementary to each other.