The detection of neural tube closure defects by exfoliative cytology of amniotic fluid.

Cytospin preparations of amniotic fluid samples from 200 pregnancies, taken between 16 and 20 weeks' gestation, were examined without knowledge of the fluid alpha-fetoprotein (AFP) level. The specimens were taken because of the possibility of neural tube closure defect. All but eight cases showed predominantly squamous cells, amnion cells, macrophages and blood cells. AFP levels in these fluids were within the normal range in 178 cases, unequivocal in 11, undetectable in 2 and raised in 1; none of the babies in these cases had a neural tube closure defect. In eight cases a large population of small cells with dark nuclei and a population of large, foamy macrophages were present in addition to the other cell types; all of these babies had a neural tube closure defect (five anencephaly and three anencephaly with spina bifida). This technique may provide a useful additional method of diagnosis of neural tube closure defects.