TY - CHAP M1 - Book, Section TI - Anencephaly A1 - Bianchi, Diana W. A1 - Crombleholme, Timothy M. A1 - D'Alton, Mary E. A1 - Malone, Fergal D. Y1 - 2015 N1 - T2 - Fetology: Diagnosis and Management of the Fetal Patient, 2e AB - Key PointsAccounts for approximately one-half of all cases of neural tube defects.Incidence is approximately 0.3/1000 births. Maternal risk factors include Hispanic ethnicity, pregestational diabetes, obesity, and hyperthermia.First trimester sonographic findings include a reduced crown-rump length, and the “Mickey Mouse” sign in the coronal view. Second trimester findings include an absent upper cranial vault and no cerebral tissue above the level of the orbits.Differential diagnosis includes amniotic bands, ruptured encephalocele, and iniencephaly.Approximately a quarter of affected pregnancies are complicated by polyhydramnios.Consider prenatal karyotype if associated anomalies present. If anencephaly is isolated, consider postnatal karyotype.Condition is uniformly fatal postnatally. Only 7% of fetuses die in utero.Preconceptual folic acid (4 mg/day) significantly decreases recurrence if anomaly is isolated and not due to a chromosomal or single-gene disorder. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/29 UR - obgyn.mhmedical.com/content.aspx?aid=1106396110 ER -