<prompt> Lecithin-Sphingomyelin ratio is used for:Lung maturityAge of infantKidney maturityBrain maturity  <response>: a. Lung maturityRef: Nelsons 20e p 2088-2093, Ghai 8e p 379-381By 35 wk of gestation, the lecithin: sphingomyelin L:S ratio averages about 2:1, indicative of lung maturity. 