Karyotyping of fetus can be done through all the following invasive methods except:

Fetal karyotyping can be done by Chorionic villi sampling Cordocentesis Amniocentesis Fetal skin biopsy is done to detect any chromosomal anomaly. It is done between 17-20 weeks to detect serious skin disorders like epidermolysis bullosa,oculocutaneous albinism. Ref: Williams Obs 23e pg 299-301.