Fetal macrocephaly: Pathophysiology, prenatal diagnosis and management

Macrocephaly means a large head and is defined as a head circumference (HC) above the 98th percentile or greater than +2SD above the mean for gestational age. Macrocephaly can be primary and due to increased brain tissue (megalocephaly), which in most cases is familial and benign or secondary. The latter may be due to various causes, including but not limited to communicating or non-communicating hydrocephalus, cerebral edema, focal and pericerebral increased fluid collections, thickened calvarium and brain tumors. Megalocephaly can be syndromic or non-syndromic. In the former, gyral and structural CNS anomalies are common. It is important to exercise caution when considering a diagnosis of megalocephaly due to limitations in the accuracy of HC measurement, lack of nomograms for specific populations, inconsistencies between prenatal and postnatal HC growth curves and progression over time. The degree of macrocephaly is important, with mild macrocephaly <= 2.5SD carrying a good prognosis, especially when one of the parents has macrocephaly and normal development. Cases in which the patient history and/or physical exam are positive or when parental HC are normal are more worrisome and warrant a neurosonogram, fetal MRI and genetic testing to better delineate the underlying etiology and provide appropriate counseling. What is already known about this topic?Fetal macrocephaly is a common diagnosis affecting 2% of pregnancies per definition. Its causes are numerous and its prognosis depends on the underlying etiology, degree of head enlargement, parental head circumferences and associated CNS and extra CNS findings.What does this study add?In this comprehensive review, we summarize the primary and secondary causes of fetal macrocephaly, their genetic background, prenatal management and anticipated outcome. This review provides clinicians with the current understanding needed for appropriate patient counseling.

Automated summary

Macrocephaly refers to a large head size, which can be primary or secondary. It can be caused by various factors and the prognosis depends on the specific condition, genetic factors, and central nervous system findings.