Uncultured cells in amniotic fluid from normal and abnormal foetuses.

Direct smears of uncultured amniotic fluid cells were analysed in 41 pregnancies between 17 and 22 weeks of gestation. These included 27 normal pregnancies where a healthy child was born at term, six anencephalic and five spina bifida pregnancies, and three other abnormal pregnancies. In normal amniotic fluid, epithelioid cells predominated but small numbers of histiocyte-like cells, typical macrophages and elongated cells were also present. The proportion of macrophages and elongated cells was significantly increased in all anencephalic cases. Two of the spina bifida cases also showed abnormal cellular proportions. Haemosiderin and lipid material was demonstrated in some of the cellular proportions. Haemosiderin and lipid material was demonstrated in some of the macrophages. Tissue smears and histological preparations suggest that these cells may originate from both the amnion and the fibrovascular membrane covering the neural lesion. This direct method of observation of amniotic fluid cells, not involving culture techniques, could provide a rapid means of prenatal diagnosis of anencephaly, and may help in the diagnosis of spina bifida.