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Clinical Review Science, Medicine, and the Future

Cell-free fetal DNA and RNA in maternal blood: implications for safer antenatal testing

BMJ 2009; 339 doi: (Published 06 July 2009) Cite this as: BMJ 2009;339:b2451
  1. Caroline F Wright, head of science1,
  2. Lyn S Chitty, reader and consultant in genetics and fetal medicine 23
  1. 1PHG Foundation, Strangeways Research Laboratory, Cambridge CB1 8RN
  2. 2Clinical Molecular Genetics, Institute of Child Health, London WC1N 1EH
  3. 3Fetal Medicine Unit, Elizabeth Garrett Anderson Wing, University College Hospital, London NW1 2BU
  1. Correspondence to: C F Wright caroline.wright{at}
  • Accepted 27 April 2009

Summary points

  • Cell-free fetal DNA (and RNA) found in maternal blood during pregnancy can be used for non-invasive prenatal diagnosis of specific genetic traits

  • Potential applications include determining fetal sex, diagnosing certain single gene disorders, fetal blood genotyping, and screening for Down’s syndrome

  • Specialist centres already offer non-invasive determination of fetal sex and RHD typing for high risk pregnancies, and the technique will probably become widely available for other indications in three to five years

  • This technology offers safer, earlier, and easier antenatal testing than current standard practice but raises ethical, legal, and social concerns, including those around informed consent and equity of access

  • Research into non-invasive prenatal diagnosis is ongoing, and the public and healthcare professionals must be kept informed about the progress and limitations of this technology

The landmark discovery that cell-free fetal DNA circulates in maternal blood during pregnancy has stimulated research worldwide into many potential applications in obstetric care.1 Improvements in molecular genetic technology over the same period have enabled the translation of cell-free fetal DNA testing into clinical practice for early non-invasive prenatal identification of some genetic traits. However, complex wider ethical, legal, and social problems associated with the technology, as well as implications for clinical and laboratory services, still need careful consideration. This article gives an overview of recent developments in cell-free fetal nucleic acid technology and its implications for non-invasive prenatal diagnosis and screening.

Sources and selection criteria

We searched PubMed, the Cochrane Collaboration, and Science Direct using the terms “non-invasive prenatal diagnosis” and “free fetal DNA” (and common variations), in addition to using personal archives of references. We also led a working group of experts and key stakeholders in the United Kingdom to review the area and make recommendations for implementation of this technology in the NHS.

What are the drawbacks of current prenatal diagnostic tests?

Prenatal screening and diagnosis form a routine part of antenatal …

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