Genetic amniocentesis is the procedure used to obtain amniotic fluid, which contains fetal skin cells. These cells are then used to check the baby's chromosomes for Down syndrome and other chromosomal anomalies. Amniocentesis is performed at 16 weeks or later and has a risk for pregnancy loss of 1 in 300. When amniocentesis is done before 16 weeks, the risk of pregnancy loss can be as high as 3.4 %. CVS is done at 12 weeks and is as safe as amniocentesis. At KOFINAS PERINATAL we offer both procedures but we prefer CVS, because in our experience the benefits of CVS outweigh those of amniocentesis. We do not use amniocentesis for the prenatal diagnosis of spina bifida. This condition can be reliably diagnosed only with ultrasound. After the ultrasound, an amniocentesis is then performed to check the chromosomes since such fetuses may suffer from chromosomal anomalies as well.