Professional
Technical
IVT
lecithin-sphingomyelin ratio
Pronunciation: LEH-si-thin SFING-go-MY-eh-lin
Laboratory test measuring fetal lung maturity by analyzing phospholipids in amniotic fluid.
Full Definition
The lecithin-sphingomyelin ratio (L/S ratio) is a biochemical test performed on amniotic fluid to assess fetal lung maturity before delivery. Lecithin and sphingomyelin are phospholipids present in surfactant, which is essential for lung function after birth. As pregnancy progresses, lecithin levels increase while sphingomyelin remains relatively constant. An L/S ratio of 2:1 or greater typically indicates fetal lung maturity and reduced risk of respiratory distress syndrome in the newborn.
Usage
Usage note: Use L/S ratio abbreviation after first mention; critical for timing elective deliveries before 39 weeks.
In Context
- "Amniocentesis revealed an L/S ratio of 2.5, indicating fetal lung maturity." — Laboratory report
- "The lecithin-sphingomyelin ratio was immature at 1.8." — Preterm delivery planning
Also known as
L/S ratio
lung maturity test
Don't confuse with
phosphatidylglycerol test
surfactant/albumin ratio