Amniotic fluid optical density and neonatal respiratory outcome.

A simple, rapid, economical, and accurate test to assess fetal pulmonary maturity on a 24-hour basis, 7 days a week, is urgently needed. A 15-minute test has been developed that correlates well with fetal pulmonary maturity. Optical density (OD) readings at 650 nm of greater than or equal to 0.15 in pigment-free, centrifuged (2000 Xg, 10 minutes) amniotic fluids obtained from gestations of 33 to 42 weeks correlate with fetal pulmonary maturity (131 of 131, 100%). When OD readings are less than 0.15 in fluids from gestations of 24 to 40 weeks, and antepartum steroids are utilized, the incidence of respiratory distress syndrome (RDS) is 8.3% (14 of 169). The true false-negative rate in this group is therefore unknown.