Maturity of fetal lungs determined by bubble stability in amniotic fluid.

A simple and quick screening method to determine fetal lung maturity is tested. Artificial air bubbles in amniotic fluid are measured microscopically in a moist chamber. Thus the concentration of the lung surfactant is evaluated and presented by the stability index (SI). This index increases continuously during pregnancy and is used as a means to determine fetal lung maturity. The large standard deviation of the SI between 30 and 35 weeks gestation limits the application of this simple method.