amniocentesis
Concise Oxford English Dictionary © 2008 Oxford University Press:
amniocentesis /ˌamnɪəʊsɛnˈtiːsɪs/
▶noun (pl. amniocenteses /-siːz/) a process in which amniotic fluid is sampled using a hollow needle inserted into the uterus, to screen for abnormalities in the developing fetus.
'amniocentesis' also found in these Oxford entries:

