BACKGROUND AND PURPOSE:

• While NIPS (NIPT) may have perceived benefit of no risk of fetal loss, it is not diagnostic
• Invasive testing is diagnostic and current risk of loss is substantially less than previously reported (see ‘Related ObG topics below)
• Guidelines recommend women be offered invasive testing following an initial ‘high risk’ standard screen for Down syndrome (trisomy 21)
• Cheng et al. (BJOG, 2017) sought to determine whether women who were screen positive (high or intermediate risk) for Down syndrome following standard screening and appropriate counseling would opt for NIPS or invasive testing

METHODS:

• Prospective cohort study
• Inclusion: Women with high risk (term risk ≥ 1:250) or intermediate risk (term risk between 1:251-1:1200) standard screening results for Down syndrome
• Exclusion: Multiple or  non-viable  pregnancies; fetuses  with  structural  abnormalities  or hydrops  at  the  time  of  screening; already  had a  private  self-financed  NIPS
• Women at high risk were given the following options
  • Diagnostic invasive test/chromosomal microarray
  • NIPS to detect trisomies 13, 18 and 21
  • Decline further testing
• Women at high risk received standardized counseling, including need to confirm positive NIPS results; procedure miscarriage risk was described as 0.1-0.2%
• Women with intermediate risk (IR) between 1:251 -1:1200 were offered NIPT as a secondary screening test
• Testing options were free and wait time for results were equivalent
• The primary outcome was NIPS uptake rate

RESULTS:

• 99.1% of 347 of women with high risk results opted for follow-up testing
• 216 women (62.2%) chose NIPS
• Only factors correlated with women opting for microarray were
  • Down syndrome risk between 1:2 to 1:9 compared to those with a risk between 1:10 to 1:250
  • Nuchal translucency ≥3.5mm
• 507 (82.6%) of 614 women with IR risk chose NIPS
  • NIPS detected one additional case of trisomy 18 and Trisomy 21, but also missed one case of Trisomy 18 and Trisomy 21

CONCLUSION:

• Even when cost is not an issue, 60% of women at high risk for Down syndrome still chose a noninvasive, non-diagnostic, less comprehensive option

Learn More – Primary Sources:

Women’s Preference For Non-Invasive Prenatal DNA Testing (NIPT) Versus Chromosomal Microarray After Screening For Down Syndrome: A Prospective Study.

Related ObG Topics:

Down Syndrome / Trisomy 21: Clinical Findings and Prenatal Considerations

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

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