Chorionic villous sampling is useful in all the following EXCEPT (AIIMS Nov 2010)
1. Chorionic villous sampling (CVS) is generally performed at 10 to 13 weeks.
a. Second trimester amniocentesis - for genetic diagnosis is usually performed between 15 and 20 weeks.
b. Early amniocentesis - this is performed between 11 and 14 weeks CVS for trophoblastic cells (derived embryologically from the same fertilized eggs as the fetus is usually done during gestational weeks 11-13
2. The advantage of CVS is that the results are available early in pregnancy
3. Indications - Advanced maternal age (> 35 years), previous child with chromosomal abnormality, abnormal parenteral karyotype, inversion, balanced or reciprocal translocation, Robertsonian, foetal karyotyping for X-linked disorder, maternal anxiety, inborn error of metabolism.
4. Lipid storage disease - Gaucher's disease, Fabry disease. Krabbe disease metachromatic leukodystrophy, Niemann Pick's syndrome mucolipidosis II sialidosis
5. Mucopolysaccharide disorder- Hunter, Hurler and Sanfilippo syndrome
6. Carbohydrate disorder - galactosemia, glyco eft storage (type n & IV) Aminoacidopathies - Homocystinuria, cystinosis, tyrosinemia, maple syrup urine disease. Autosomal dominant disorders - adult polycystic kidney disease. myotonic dystrophy, Huntington's chorea, osteogenesis imperfecta, retinoblastoma
7. Autosomal recessive disorders - a and β thalassanemia, al antitrypsin deficiency, CAH, phenylketonuria, cystic fibrosis sickle cell disease
8. Sex linked disorders - Duchenne's A & B, chronic granulomatous disease, Norrie's disease, retinitis pigmentosa
9. Relative contraindications
a. Vaginal bleeding or spotting
b. Extreme ante-or retroversion of the uterus
c. Patient body habitus precluding easy access to the uterus
d. Active infection.