[Microcephaly diagnosed during pregnancy]

Microcephaly is defined postnatally as small head circumference (below the norm by more than two standard deviations (SD)). Incidence at birth: 1:6250-8500. The prenatal diagnosis of microcephaly, particularly in cases of primary microcephaly, is usually difficult before the 3rd trimester. Congenital microcephaly may present as an isolated finding, in this case it is known as primary microcephaly or microcephaly vera and may also be associated with a wide range of central nervous system (CNS) and non-CNS pathologies. The association between microcephaly and intellectual capabilities has frequently been searched but there is no definite correlation with prenatal diagnosis of microcephaly. Postnatally, the risk for developmental disabilities for microcephaly is 11% when head circumference is -2SD, 50-75% in -3SD and 100% when head circumference is smaller than -4SD. The lack of knowledge regarding the prognosis when microcephaly is found during pregnancy makes counselling difficult. In this review, the authors describe and define microcephaly and the association with intellectual disabilities, emphasizing the importance of prenatal diagnosis.