A study of the procoagulant properties of amniotic fluid and their correlation with the lecithin/sphingomyelin ratio.

The procoagulant properties of amniotic fluid have been studied in samples taken throughout pregnancy and the results correlated with the lecithin/sphingomyelin ratio: acceleration effects on the prothrombin time. Russell's viper venom test, activated partial thromboplastin time and specific factor VII and X assays and contact acceleration. Although amniotic fluid is shown to function as a complete thromboplastin and to activate factor X directly, none of these tests of procoagulant activity of amniotic fluid is a reliable index of fetal lung maturity.