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Expert recommendations for earlier, safer prenatal diagnosis

16 February 2009
By Dr Philippa Brice
Head of Knowledge and Communications, PHG Foundation
Appeared in BioNews 495
Cell-free fetal nucleic acids - DNA or the related molecule RNA - are present in the blood. As has previously been reviewed, the discovery that a small proportion of the cell-free nucleic acids in the mother's blood during pregnancy actually comes from the fetus paved the way for new techniques to exploit this as a non-invasive prenatal diagnosis. A new report from a UK expert Working Group funded and led by the PHG (Public Health Genetics) Foundation presents a review of the current clinical and scientific status of these rapidly developing technologies, along with ethical, social and legal implications of different applications, and key issues associated with implementation in the NHS.

Fetal DNA can be reliably detected from 7 weeks gestation, and is lost from the maternal blood within a few hours of birth; the key technical problem is in reliably distinguishing it from that of the mother. However, applications for which the technology can be used already or is likely to become feasible soon include the identification of various fetal traits: fetal sex (important for rare inherited diseases that affect only one sex); fetal RhD blood-group status (important in RhD-negative mothers at risk of dangerous reactions caused by RhD-positive fetuses); mutations that cause certain specific inherited diseases, especially where inherited from the father; and chromosomal aneuploidies such as Down's syndrome.

Detection of fetal characteristics in this manner represents an important improvement over current, invasive methods of testing (amniocentesis or CVS, (chorionic villus sampling) because it is possible much earlier in pregnancy (from 7 weeks, compared with 11-16 weeks for invasive testing) and carries no associated risk of miscarriage, compared with a risk of around 1% for amniocentesis and CVS. Invasive testing causes the loss of several hundred pregnancies each year in the UK, and many women at high risk of having a fetus affected by genetic or chromosomal disease opt against it because of the risk to the fetus.

The new PHG Foundation report is the product of an expert Working Group, which included general and specialist clinicians (GPs, obstetricians, midwives and geneticists), scientists, NHS commissioners, public health experts, ethicists and patient representatives. As well as looking at the technology and the likely timescales for possible introduction as an NHS service, the group also looked at some of the potential ethical, social and legal implications of the technology. Key ethical challenges to implementation were found to include the importance of safeguarding patient autonomy and providing for informed consent; ensuring equity of access; and ensuring that use of the technology should be restricted to important clinical applications. Non-clinical applications such as social sex selection and paternity testing were identified as potential problems arising from commercial provision of testing services direct to the public, raising the issue of whether regulation was required in this area.

The working group concluded that the implementation of non-invasive prenatal diagnosis in the NHS for clinically significant genetic disorders is desirable to improve the quality and management of antenatal care, and to facilitate parental reproductive choice. However, a number of issues must be addressed before the technology could be widely introduced in the NHS. The main findings of the group were:

  • Reliable non-invasive prenatal diagnosis using fetal DNA is already possible for some applications and likely to become available for others within the next 3-5 years.
  • The NHS should take steps now to ensure that it is able to respond in a timely and appropriate manner as the technology develops. This includes formal evaluation for different purposes, development of specified care pathways and national best practice guidelines, and oversight from the appropriate authorities.
  • Both public engagement efforts and health professional education about the potential and limitations of the technique are urgently needed.
  • The technique should only be used according to standardized protocols within agreed clinical pathways, with formal audit and monitoring processes, and quality assurance frameworks. This will ensure appropriate use and accurate, reliable results.
  • Non-invasive prenatal diagnosis is already available privately on a direct-to-consumer basis, and may have an increasing impact on NHS primary care and antenatal services. A voluntary code of conduct should be supported to help ensure the quality of private services.
  • Ethical and social issues associated with some of the broader implications of non-invasive prenatal diagnosis using fetal DNA warrant further consideration and research.

The report and recommendations, along with a separate appendix dealing with ethical, legal and social issues, is available for free download from the PHG Foundation website.

SOURCES & REFERENCES
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