What Is the Lecithin-Sphingomyelin Ratio?
Early pregnancy: <1: 1; full-term pregnancy: <2: 1.
- The amniotic fluid contains about 500mg / L of fat and about 40mg / L of phospholipid. In early pregnancy, there are many sphingomyelin, and its content does not change significantly throughout pregnancy. The content of lecithin as an alveolar surfactant is similar to sphingomyelin before 34 weeks of gestation, and it increases sharply after 34 weeks of gestation, so that the lecithin / sphingomyelin ratio is above 2 and this value can be regarded as fetal lung Maturity value. Fetal mature fetuses rarely develop respiratory distress syndrome after birth.
- Name
- Amniotic fluid lecithin / sphingomyelin ratio
- category
- Biochemical tests
Normal amniotic fluid lecithin / sphingomyelin ratio
- Early pregnancy: <1: 1; full-term pregnancy: <2: 1.
Clinical significance of amniotic fluid lecithin / sphingomyelin ratio
- (1) L / S> 2: The lungs are mature and the fetus does not have acute respiratory distress syndrome. (2) L / S <1.5: Lungs are immature and a significant number of fetuses develop acute respiratory distress syndrome. (3) L / S 1.5-1.9: Intermediate type, a few fetuses develop acute respiratory distress syndrome. The L / S ratio is affected by the following factors: (1) accelerated lung maturation: hypertension, kidney disease, diabetes, sickle cell anemia, premature separation of the placenta (early stripping of the placenta), water breakthrough for more than 36 hours, intrauterine blood transfusion, use Glucocorticoids. (2) Lung maturity retardation: neonatal edema (fetal edema), diabetes.
Notes on amniotic fluid lecithin / sphingomyelin ratio
- Except for premature babies who are susceptible to RDS, the L / S ratio of some newborns in pregnant women with diabetes is greater than 2, but the incidence of RDS is higher than that of normal pregnant women. This should not be ignored.