What it means
Lecithin and sphingomyelin are parts of surfactant, the substance that keeps the tiny air sacs of the lungs open. Late in pregnancy the lungs make much more lecithin, so the ratio rises. A ratio of 2:1 or more in fluid taken by amniocentesisam-nee-oh-sen-TEE-sisA test in which a needle is put through the belly into the uterus to take a sample of amniotic fluid.amni/o amnion (the sac around the fetus)-centesis puncture to remove fluidFull entry suggests the lungs are mature and the baby is less likely to have breathing trouble after birth. Babies of parents with diabetes may need a higher ratio.
At a glance
| Normal range | 2:1 or higher indicates lung maturity |
|---|---|
| Also written | L/S ratio, lecithin-sphingomyelin ratio |
Related terms
alveolus
One of the tiny air sacs at the ends of the smallest airways in the lungs.
amniocentesis
A test in which a needle is put through the belly into the uterus to take a sample of amniotic fluid.