What is amniocentesis? Amniocentesis is a method of prenatal diagnosis that involves puncturing the uterine cavity, using a needle to penetrate the amniotic fluid sac from the vagina, and removing the amniotic fluid from the fetus for testing. Performed between 16 and 24 weeks of pregnancy, it can detect fetal chromosomal abnormalities, neural tube defects, metabolic diseases, genetic diseases and other diseases. What abnormalities can amniocentesis detect? 1. Chromosomal abnormalities: Amniocentesis can clearly diagnose some chromosomal defect diseases, such as Down syndrome, Edwards syndrome, Plucker syndrome, etc., and can also detect pregnancy.