All of the following are done for Karyotyping of fetus except: (AIIMS MAY 2011)
a. Amniocentesis for genetic diagnosis usually is performed between 15 and 20 weeks. In the United States, it is the procedure most commonly used to diagnose fetal aneuploidy and other genetic disorders.
b. Problems includes vaginal spotting or amnionic fluid leakage in 1 to 2 percent and chorioamnionitis in less than 0.1 percent. Needle injuries to the fetus are rare.
1. Early Amniocentesis
2. Chorionic Villous Biopsy
b. The primary advantage of villous biopsy is that results are available earlier in pregnancy, which lessens parental anxiety when results are normal. It also allows earlier and safer methods of pregnancy termination when results are abnormal.
c. Early reports of an association between CVS and limb-reduction defects and oromandibular limb hypogenesis.
3. Fetal Blood Sampling
a. Also called percutaneous umbilical blood sampling (PUBS) or cordocentesis,
b. This is a noninvasive method of detecting severe fetal anemia, used prior to proceeding with fetal blood sampling and/or intrauterine transfusion. Fetal blood sampling also can be used to obtain cells for genetic analysis when CVS or amniocentesis results are confusing or when rapid diagnosis is necessary. Karyotyping of fetal blood usually can be accomplished within 24 to 48 hours.
c. Problems includes vessel Bleeding and hematoma formation.
4. Fetal Tissue Biopsy
a. There are many genetic conditions for which there is no specific molecular test. Sometimes, prenatal diagnosis can only be accomplished by direct analysis of fetal tissue obtained by sonographically guided biopsy. Linkage analysis has been used for the diagnosis of familial disorders, but it is possible only if there are living.
b. The technique has been used for muscle biopsy to diagnose muscular dystrophy or mitochondrial myopathy and skin biopsy has been used to diagnose epidermolysis bullosa