Chorionic villus sampling
(CVS) done between 11-14 weeks
CVS involves the examination of chorionic villi (placental tissue). Both the baby and placenta (after birth) originate from the same cell and so the chromosomes present in the cells of the placenta are the same as those of the baby.
Amniocentesis done between 15-20 weeks
Amniocentesis involves passing a thin needle into the uterus in order to remove fluid from around the fetus. Results are known in 2-3 weeks
Fetal blood sampling or Cordocentesis
Fetal blood sampling involves passing a thin needle into the uterus down to the umbilical cord where it attaches to the placenta. A small amount of blood is taken for the test and the results are known within 4-5 days.
All these procedures are done under constant ultrasound
guidance, but a 0.5-1 % risk of miscarriage is
reported globally in these procedures.
