Estimation of fetal maturity by cytologic examination of amniotic fluid

Abstract

The cellular content of amniotic fluid is primarily composed of desquamated fetal cells of two origins, squamous and sebaceous, readily differentiated by staining with Nile blue sulfate. The squamous cells are histologically distinctive and stain light blue with dark blue nuclei. A smaller number of lipid-containing cells, shed from sebaceous glands, are different in structure and stain orange to pink in color. The percentage of such “fat cells” in the amniotic fluid, reflecting progressive development of sebaceous glands, increases with advancing gestational age. Three hundred and fifty specimens of amniotic fluid were obtained at various stages of gestation, stained for fat, and a differential cell count performed. There was a reliable logarithmic augmentation of fat cells with increasing fetal age and development. When their count was less than 2 per cent, the prematurity rate was 85 per cent. When the fat cell count exceeded 20 per cent, all infants weighed over 2,500 grams and had a gestational age of 36 weeks or more. When the need to determine fetal age exists, particularly if there is either an unreliable menstrual history or controversial physical findings, this means of its estimation is as reliable as other presently used methods, including radiography.