A

Acetylcholinesterase in amniotic fluid is a highly specific marker for open neural tube defects—especially open spina bifida—because the exposed neural tissue releases this enzyme into the fluid; ventral abdominal wall defects (gastroschisis, omphalocele) and bone disorders do not. [Burton, 1986, PMID 2946231] [Rasmussen Loft et al., 1990, PMID 2146603]