During Her Second Trimester of Pregnancy a 31-Year-Old Woman Visits

During her second trimester of pregnancy a 31-year-old woman visits her obstetrician for an ultrasound scan. The obstetrician explains to the woman that several vertebral arches have not formed and a fluid-filled cyst is protruding from the lumbosacral region of the fetus. An in utero surgery is scheduled for the third trimester. Which of the following most accurately characterizes these birth defects?

A) Anencephaly
B) Microcephaly
C) Spina bifida cystica
D) Aqueductal stenosis
E) Hydramnios