Risk of respiratory distress syndrome as determined by amniotic fluid lecithin concentration.

Lecithin concentration has been determined in 476 samples of amniotic fluid collected within 72 hours of delivery. If delivery is associated with a level of lecithin of 0.100 mg/100 ml. of lecithin phosphorus or greater, the risk of RDS in the neonate is minimal, if any. If delivery is associated with a level of lecithin less than 0.100 mg/100 ml. of lecithin phosphorus, a definite risk of RDS is present. This "risk factor" is a function of the lecithin concentraion and may be expressed in terms of a simple mathematical equation. The equation, log y equals minus 1.0187 minus 0.0101 chi, expresses the relationship in a highly significant manner (r equals 0.99) where y equals lecithin concentration and chi equals risk of RDS. In managing individual high-risk patients, our general policy is to weigh the chemically determined "risk factor" of RDS if delivery is done against the clinically determined "risk factors" involved if delivery is delayed. By comparing the various risks involved, appropriate management is decided upon.