During her eighth month of pregnancy, a 29-year-old woman is noted to have polyhydramnios. Further testing shows anencephalus. Polyhydramnios in this patient is caused by which of the following?
Anencephalus is due to failure of the cephalic part of the neural tube to close off. This condition happens in 1/1000 pregnancies, is four times more common in whites than blacks, and is four times more common in females than males.
Impairment of the fetus's swallowing mechanism
Tumor of the fetus's brain
A secretory peptide from the placenta
Excess antidiuretic hormone (ADH) from the fetus
Urethra & Penis