Abstract
The ratio of lecithin to sphingomyelin (L/S) in amniotic fluid was assessed in 209 patients on 275 occasions and confirmed to be a useful index of fetal lung maturity.
Although low and high ratios were found mainly at early and late gestational ages respectively, lung maturity (L/S ratio ≥ 3:1) occurred at a wide range of ages, from 28 to 40 weeks. The L/S ratio was, therefore, not found to be a useful index of gestational age in individual cases.
In 174 cases, in addition to determining the L/S ratio, the concentration of creatinine in the liquor was estimated as an index of renal maturity. (Creatinine ≥ 1.6 mg./100 ml. ≡ renal maturity). In 80 per cent of cases, lung and kidney were judged to be both mature or both immature. In the remainder, combinations of mature kidney/immature lung or immature kidney/mature lung existed. Liquor creatinine estimation remains useful as a guide to gestational age and as an adjunct to lung maturity studies.
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