GROSS ANATOMY Supratentorial Structures • Gyri : Complex convolutions of brain cortex; hypoechoic on US • Sulci (fissure): Cerebral spinal fluid (CSF)-filled grooves or clefts that separate gyri; echogenic on…

KEY FACTS Terminology • 70% dizygotic : 2 ova fertilized by different sperm; therefore, all are dichorionic • 30% monozygotic : Single ovum fertilized by single sperm, which then divides…

KEY FACTS Imaging • Holoprosencephaly is hallmark anomaly ○ Spectrum of severity: Alobar, semilobar, lobar ○ Associated facial anomalies – Close-set orbits (hypotelorism), fused eyes (cyclopia) – Small nose, proboscis…

KEY FACTS Terminology • Fibroid, leiomyoma • Definition: Benign smooth muscle tumor of uterus Imaging • Typically well-defined round or oval hypoechoic mass ± calcification • Myomas can grow during…

KEY FACTS Terminology • Spectrum of congenital uterine malformations ○ 20% unicornuate : Single uterine horn ± rudimentary horns ○ 5% uterus didelphys : 2 separate horns, 2 cervices –…

KEY FACTS Terminology • Autosomal trisomy of chromosome 18 (T18) Imaging • Hallmark finding: Multiple anomalies ○ No single anomaly is hallmark of T18 • Most cases with findings at…

KEY FACTS Terminology • Monochorionic (MC) twin complication caused by intrauterine transfusion of blood from donor twin to recipient twin via arteriovenous placental anastomoses Imaging • Hallmark finding is oligohydramnios…

KEY FACTS Imaging • Fetal growth restriction • Brain findings ○ Microcephaly (up to 27%) ○ Ventriculomegaly (moderate to severe in 45%) – Intraventricular adhesions, abnormal periventricular echogenicity – Periventricular/parenchymal…

KEY FACTS Imaging • Germinal matrix hemorrhage (GMH) most common at caudothalamic (CT) groove in vascular germinal matrix • Grading system ○ Grade 1 : GMH only with globular echogenic…

KEY FACTS Imaging • Nonrandom association of 6 core abnormalities ○ V ertebral defects – Hemivertebrae: Best demonstrated in coronal plane, scoliosis originates at hemivertebra(e) – Fusion of vertebral bodies…