BACKGROUND AND PURPOSE:

• More recent cohort population studies and RCTs suggest that previous risk for miscarriage following prenatal invasive genetic testing may be overstated
• Salomon et al. (Ultrasound in Obstetrics & Gynecology, 2019) sought to estimate procedure-related risk of miscarriage after amniocentesis and chorionic villus sampling (CVS)

METHODS:

• Systematic review and updated meta-analysis
• Inclusion criteria
  • RCTs | Prospective or retrospective cohort or case-control studies
  • Results included complications following CVS or amniocentesis and pregnancy loss <24 weeks 
• Data analysis
  • Procedure-related risk of miscarriage was estimated as a weighted (based on sample size of each study) risk difference
  • Subgroup analysis also performed

RESULTS:

• 20 controlled studies were included
• Risk of miscarriage after amniocentesis
  • Miscarriage group: Risk of pregnancy loss of 0.91% (95% CI, 0.73 –1.09)
  • Control group: Pooled loss rate of 0.58% (95 CI%, 0.47–0.70)
  • Pooled weighted procedure-related risk of miscarriage: 0.30% (95% CI, 0.11–0.49)
  • Using only studies with similar patient risk profiles: Procedure related risk was 0.12% (95% CI, -0.05 to 0.30)
• Risk of miscarriage after CVS
  • Groups
  • CVS group: a risk of pregnancy loss of 1.39% (95% CI, 0.76–2.02)
  • Control group: Risk of pregnancy loss of 1.23% (95 CI%, 0.86–1.59)
  • Pooled weighted procedure-related risk of miscarriage: 0.20% (95% CI, -0.12 to 0.52)
  • Using only studies with similar patient risk profiles: Procedure related risk was was -0.1 (95% CI, -0.29 to 0.08)

CONCLUSION:

• When studies are restricted to patients with similar risk profiles, the authors conclude

…amniocentesis is associated with a procedure-related risk of 1:300 at most, or more likely, no significant increase in risk

With regard to CVS, our results demonstrate that, there is no significant procedure-related risk associated with undertaking this procedure

• The authors suggest a few reasons why CVS may be safer than amniocentesis including
  • CVS performed by trained MFM experts
  • Amniotic sac is a ‘closed cavity’ vs the highly vascular placenta at 12 weeks
  • When CVS is more challenging, the operator may choose to defer to amniocentesis, thus biasing amniocentesis toward more difficult cases

Learn More – Primary Sources:

Risk of miscarriage following amniocentesis or chorionic villus sampling: systematic review of the literature and updated meta‐analysis

Related ObG Topics:

Should Amniocentesis or Chorionic Villus Sampling Be Offered to All Pregnant Women?

Does Noninvasive Screening Result in Fewer Miscarriages When Compared to Amniocentesis?

Fetal loss after amnio or CVS – what is the risk ?

Invasive Testing: Are All Centers Seeing a Similar Steep Decline in Procedures?