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

fetal skin injuries due to amniocentesis might be rapid and complete. We would like to describe the procedures of fetal skin biopsy which may serve as a tool for prenatal detection of congenital defects. The pregnant woman lies supine. Guided by palpation and fixation of the fetus with assistant's hands, the Vim-Silverman biopsy needle with the obturator is introduced through the abdominal and uterine walls on the median line between symphysis and navel. When the needle is advanced slightly into the fetal tissue, the obturator is replaced with the inner split needle. Several pieces of fetal skin (about 1 mmX2 mm in size) are obtained by repeated splitting with the inner needle. So far this procedure has been tried for eight women who were in the second or third trimester of pregnancy