The amniotic fluid contains squamous epithelial cells and anucleated fat cells. The relative number of fat cells increases as the fetus develops. The results correlate with gestational age but not necessarily with fetal lung maturity.


Specimen: Amniotic fluid, protected from light.


Testing: Stain amniotic fluid with Nile blue.


percentage of fat cells =

= (number of fat cells) / (total cells)



• more than 50% fat cells indicates that the fetus is mature



• Maternal diabetes can cause false positive elevation in percentage of fat cells.


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