Chorionic villus biopsy is done in all of the following EXCEPT:

Ans. A. Neural tube defectsa. Indications of Chorionic villus biopsy:i. Karyotyping is the most common indication--Down syndromeii. Hemoglobinopathies --Sickle cell disease, Thalassemia, etc.iii. Biochemical studies--Gaucher's disease, Niemann-Pick disease, Tay-Sachs' disease, etc.iv. Single gene defects--Myotonic dystrophy, Cystic fibrosis, Huntington's disease, Phenylketonuria, etc.b. Neural tube defects are diagnosed by ultrasound and estimation of alpha-fetoprotein in maternal serum/amniotic fluid.c. Chorionic villous biopsy can be done after 10th week (earlier than amniocentesis) i. Earlier results reduce maternal stress by going for a possible therapeutic abortion (if indicated) at an early stage.d. Initially a trans-cervical route is acceptable to take the sample.i. A trans-abdominal route is taken if the pregnancy exceeds 12th week.