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  3. Non-invasive prenatal testing for aneuploidy screening
Practice Rational Testing

Non-invasive prenatal testing for aneuploidy screening

BMJ 2020; 371 doi: https://doi.org/10.1136/bmj.m3930 (Published 27 October 2020) Cite this as: BMJ 2020;371:m3930
  1. Rebecca Spencer, clinical lecturer in obstetrics and gynaecology and subspecialty trainee in maternal and fetal medicine1,
  2. Hilary Hewitt, screening coordinator and fetal medicine midwife2,
  3. Laura McCarthy, GP and a previous trainee in obstetrics and gynaecology3,
  4. Ruwan Wimalasundera, consultant obstetrician and fetal medicine specialist2,
  5. Pranav Pandya, consultant obstetrician and fetal medicine specialist, chair of the Fetal Anomaly Screening Programme Advisory Group2
  1. 1Fetal Medicine Unit, Leeds General Infirmary and University of Leeds, UK
  2. 2Fetal Medicine Unit, University College London Hospitals, UK
  3. 3Sunnybank Medical Centre, Wyke, Bradford
  1. Correspondence to: R Spencer r.n.spencer{at}leeds.ac.uk

What you need to know

  • Non-invasive prenatal testing (NIPT), which relies on fragments of DNA from the placenta, is a screening test for fetal aneuploidy with high negative predictive rates, making it a valuable alternative to combined or quadruple screening

  • NIPT can either be offered to all pregnant women as a primary screening test or contingent on initial combined or quadruple screening

  • Unbiased information on the conditions being screened for, as well as the advantages and limitations of different screening approaches, is essential for women to make an informed choice

A 36 year old woman attends her general practice at 8 weeks in her second pregnancy. She has heard there is a new blood test she can have which will test for chromosomal anomalies and wants to find out more.

Aneuploidy screening

In many countries, screening for trisomies 21 (Down’s syndrome), 18 (Edward’s syndrome), and 13 (Patau’s syndrome) is offered as part of routine antenatal care. This can be performed from 11+2 to 14+1 weeks’ gestation using combined screening (nuchal translucency, pregnancy-associated plasma protein A (PAPP-A), human chorionic gonadotrophin β subunit (βHCG) and maternal age) or from 14+2 to 20+0 weeks using quadruple screening (βHCG, unconjugated oestriol, α-fetoprotein and inhibin A). About 3% of women will receive a “high chance of trisomy” result from one of these screening tests and are traditionally offered an invasive procedure to confirm the result—either chorionic villus sampling (from 11+2 weeks) or amniocentesis (from 15+0 weeks). The disadvantage of these invasive procedures is the procedure-related risk of miscarriage of about 0.3%.1 Non-invasive prenatal testing (NIPT) is a newer screening test with high detection rates and low false positive rates.

Whether or not a pregnant woman chooses to have aneuploidy screening, the first trimester ultrasound scan remains an important test for dating the pregnancy and diagnosing multiple pregnancy, missed miscarriage, and early …

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