Assessment of fetal maturation by the foam test

The foam test, performed in 66 high-risk pregnancies, has been shown to diagnose fetal maturity reliably only when it was “positive.” When the test was negative, the fetus, in 73.3 per cent of the cases, was premature, and the incidence of hyaline membrane disease was similar to that observed in premature fetuses of similar gestational age. An intermediate result in the test detected fetal maturity in 80 per cent of the cases and was not associated with hyaline membrane disease. Although a positive foam test correlated significantly with the concentration of amniotic fluid lecithin, tests with positive, intermediate, and negative results were found at lecithin concentrations lower than 180 μg per cent. This observation opens to question the validity of the test as an indirect measurement of lung surfactant material. The foam test, being economical, reliable, and fast, should replace the lecithin-sphingomyelin ratio test.