This blog post is a Summary of Green Top Guideline 8: Amniocentesis and Chorionic Villous Sampling which was updated in October 2021. As it is a GTG so, it is must to go through the full guideline by yourself in order to have the complete understanding.
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Background
- Prenatal diagnosis in the form on amniocentesis or CVS is offered due to various reasons such as higher risk for aneuploidy screening, suspected structural anomaly or in cases of known risk of inherited genetic disease
- The only definitive diagnostic tests → both CVS & amniocentesis
- CVS done between 11+0 - 13+6 wks Can also be done 14+0 - 14+6 wks
- Amniocentesis offered from 15+0 wks
- Individualised counselling
- Informed written consent Form 3
- Must provide information for aftercare
Organising amniocentesis & CVS
- Women are usually anxious so should support them ± partners
- Follow Fetal Anomaly Screening Program guidance
- Appropriate environment, skilled staff, access to allied specialities and appropriate support for continuation or termination of pregnancy
- Sensitive & unbiased approach
- Discuss religious aspects
- Give time to discuss the decision with partners & friends
Additional Risks with Invasive Testing
Risk of Miscarriage
- Additional risk of pregnancy loss after CVS or Amniocentesis is performed by an appropriately trained operator is < 0.5%
Different studies have been quoted
- Earlier studies showed increased pregnancy loss after CVS, but later studies show that there is no significant increase in pregnancy loss above the background risk with both procedures
- Lower pregnancy loss likely due to improvements in technology, techniques & experience
Systemic Review 2000-2014
- Procedure-related risk of pregnancy loss Amniocentesis 0.11% CVS 0.22% Both 0.35%
Cochrane Review comparing route for CVS (Transabdominal or Transcervical)
- Pregnancy loss below background rate regardless of route
- Procedure-related pregnancy loss Transcervical 1.4% Transabdominal 1%
Other risks
- CVS results may be affected by placental mosaicism in 1-2%
- Structural anomaly present → Discuss ongoing care (continuation or termination of pregnancy)
- Structural anomaly absent & QFPCR after CVS suggest chromosomal anomaly → full karyotype awaited before any decision
- Severe maternal sepsis → very rare