The lecithin-sphingomyelin ratio (L-S Ratio) in the amniotic fluid surrounding the foetus in the uterus can be measured to assess foetal maturity and readiness for birth. If the ratio is high (greater than 2 to 1) the foetal lungs are mature. If the ratio is less than 2 to 1 the foetal lungs are not mature. Lecithin is a fat from the foetal lung that is produced in increasing quantities in relation to another fat, sphingomyelin, after 34 weeks of pregnancy.
(Last modified: 9th Oct 2014)