L:S ratio

(redirected from LS ratio)

L:S ra·ti·o

lecithin:sphingomyelin ratio

(les'i-thin sfing?go-mi'a-lin ra'she-o),

L:S ratio

The ratio of lecithin to sphingomyelin in the amniotic fluid. It is used to assess maturity of the fetal lung. Until about the 34th week of gestation, the lungs produce less lecithin than sphingomyelin. As the fetal lungs begin to mature, they produce more lecithin than sphingomyelin. Delivery before the reversal of the ratio is associated with an increased risk of hyaline membrane disease in the infant. The use of this test enables the obstetrician to determine the best time for elective termination of pregnancy. Other tests commonly used for this purpose include the amniotic lamellar body count, phosphatidylglycerol presence, and the shake test. See: amniocentesis
References in periodicals archive ?
It is evident from the mean values that there is a decrease in all the three parasympathetic function tests: DBT, LS ratio, and valsalva ratio among the cases as compared to controls although changes are not statistically significant (P > 0.
Thus, LS ratio data, which is only available to Springfield, Missouri observations alone, should adequately represent LS ratios for Southwest Missouri.
We tried to select fields with high cellularity, in which the XS/ LS ratio was roughly the same in both myomas of each matched pair.