Large encephaloceles can mimic anencephaly, but generally have more calvarial development. Anencephaly occurs in about 1 in 1000 births. Multifactorial inheritance with both genetic and environmental factors is implicated. Recurrence risk after one affected pregnancy is two to three percent for any open neural tube defect. Screening with maternal serum alpha-fetoprotein screening will detect most cases of anencephaly.
Pregnancy termination is offered at any gestational age.
Diagnostic Ultrasound, 2nd ed. Medical Informatics Group, Department of Radiology, University of Pennsylvania Medical Center.