NEET PG High-Yield: Amniocentesis
Amniocentesis is a vital tool for Secondary Prevention (Early Diagnosis). It involves the aspiration of amniotic fluid for genetic and biochemical analysis.
Key Procedural Details
- Timing: Traditionally performed at 15–18 weeks of gestation.
- Technique: Ultrasound-guided transabdominal aspiration of amniotic fluid.
- Safety: Low risk of procedure-related miscarriage (approximately 0.5%).
Indications for Analysis
| Category | Analysis Type |
|---|---|
| Chromosomal | Karyotyping for Down syndrome ($Trisomy\ 21$), other aneuploidies. |
| Biochemical | Alpha-fetoprotein (AFP) levels for neural tube defects. |
| Genetic | PCR/FISH for specific monogenic disorders (e.g., Cystic fibrosis). |
High-Yield NEET PG Pearls:
- Comparison: Chorionic Villus Sampling (CVS) can be done earlier (10–12 weeks) but carries a slightly higher risk of limb reduction defects.
- Rh-Immunization: Anti-D immunoglobulin must be administered to Rh-negative mothers undergoing the procedure to prevent sensitization.
- Amniotic Fluid: Contains fetal cells (amniocytes) shed from skin and respiratory/urinary tracts, which are cultured for chromosomal analysis.