5061
The relation between the choline containing surfactant phospholipids lecithin and sphingomyelin in amniotic fluid and fetal lung maturity is well established .
 amniotic fluid, fetal lung
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Anatomy 
Text: {0} 
Answer:
 amniotic fluid, fetal lung