How many weeks of pregnancy must be done for amniocentesis?

Patient's question:

No

Doctor's answer:

In the late stage of pregnancy, amniocentesis can determine blood type, bilirubin, lecithin, sphingomyelin, placental lactogen, and other markers to assess whether there is maternal-fetal blood type incompatibility, hemolysis, fetal lung maturity, skin maturity, placental function, etc. The optimal time for amniocentesis to extract amniotic fluid is between 16 and 20 weeks of gestation.