<prompt> Amniocentesis to detect chromosomal abnormalities can be done as early as14th week of gestation18th week of gestation22nd week of gestation26th week of gestation  <response>: Amniocentesis: examination of a sample of amniotic fluid makes possible the prenatal diagnosis of chromosomal anomalies and certain metabolic defects; the procedure can be used as early as 14th week of pregnancy when abortion of affected fetus is still feasible. 