The phospholipid content of lung fluid taken from 77 babies during the first day of life was studied. Babies with hyaline membrane disease had low concentrations of the surfactant phospholipids phosphatidylcholine, phosphatidylinositol, and phosphatidylglycerol. The palmitic acid content in phosphatidylcholine was also lower than normal. Surfactant deficiency was not, however, specific for hyaline membrane disease, as similar phospholipid abnormalities were observed in babies with congenital pneumonia and transient tachypnoea of the newborn.These findings have important clinical implications. They are relevant to research into surfactant substitution and cast doubts on the value of the antenatal phospholipid lung profile of amniotic fluid in predicting the risk of hyaline membrane disease.

summary The phospholipid composition of amniotic fluid samples from 30 normal patients and 44 diabetic patients over the last 10 weeks of pregnancy was studied. Higher levels of phosphatidylcholine (PC) and phosphatidylinositol (PI) were found in diabetic pregnancies where there was excellent glucose control. These differences were statistically significant at 34–36 weeks. Phosphatidylglycerol (PG) aeared significantly earlier in the well controlled diabetic pregnancies. but even in the poorly controlled diabetics the levels of PC, PI and PG were comparable to those in normal pregnancies. There was no evidence of delayed aearance of fetal surfactant phospholipids in either the well or poorly controlled diabetic pregnancies. The absolute lecithin (PC)/sphingomyelin (SM) ratio in diabetic pregnancies was generally greater for any given gestational age than those in normal pregnancies. Whilst in most cases this was due to a higher PC concentration, in a few poorly controlled diabetics it was the result of a lower concentration of SM.

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summary Fifty babies were born at ≤ 37 weeks to mothers with diabetes. Delivery was undertaken in all patients with the reassurance that the L/S ratio was ≥2.0 within the preceding 72 h. Five babies (10%) developed respiratory distress syndrome (RDS). Prediction of fetal lung maturity was improved dramatically by measuring amniotic fluid concentrations of phosphatidylcholine (PC), phosphatidylinositol (PI) and phosphatidyl‐glycerol (PG). Fourteen babies were predicted as having ‘no surfactant’ (PC < 20 mg/1, PI < 2 mg/1 and PG < 2 mg/1), five developed RDS. None of the remaining 36 babies developed the illness: they were predicted as having either ‘early surfactant’ (PC ≥ 20 mg/1, PI ≥ 2 mg/1 but PG < 2 mg/1) or ‘late surfactant’ (PC ≥ 20 mg/1, PI ≥ 2 mg/1 and PG ≥ 2 mg/1). Measurement of PC levels alone was the most accurate method of predicting RDS. There was a significant association between low surfactant phospholipid concentrations and the development of transient tachypnoea of the newborn.