182 Obstetrics and Gynecology Board Review •••
❍ At which gestational age should the fetal abdomen be intact?
12 weeks.
❍ Which anterior abdominal wall defect is associated with aneuploidy?
With an omphalocele, there is a 30% to 40% risk of aneuploidy. It is a midline defect resulting in the herniation
into the base of the cord, which is unlike gastroschisis where the herniation is lateral to the cord insertion and not
associated with aneuploidy.
❍ What is an Arnold-Chiari malformation and what is it associated with?
Displacement of the cerebellum, fourth ventricle, and the medulla. It is associated with open neural tube defects.
❍ Characteristic ultrasound findings associated with Arnold-Chiari malformation?
Lemon sign and banana sign.