<prompt> Karyotyping of a fetus is done routinely by all the following exceptChorionic villus samplingCordocentesisAmniocentesisFetal skin biopsy  <response>: Karyotyping: the Visual study of chromosomes after metaphase arrest by the use of ColchicineFetal karyotyping :1Chorionic villus sampling: Biopsy taken transcervically at 8 to 12 weeks of gestation2Amniocentesis: 20 ml of amniotic fluid is aspirated at 14 to 20 weeks of gestation3Cordocentesis not preferable: Fetal blood aspirated from the umbilical cord after 18weeks of gestationRef: Kawthalkars essentials of hematology 2e p162 