Non-invasive prenatal testing (NIPT) is likely to become a primary screening method for chromosomal abnormalities (such as Down syndrome) in pregnancy in the future and so greatly reduce invasive testing and the associated risks, says a new Scientific Impact paper published today by the Royal College of Obstetricians and Gynaecologists (RCOG).
The Scientific Impact Paper (SIP) looks at the issues surrounding this new technology including what it currently is used for and comparisons with invasive testing.
SIPs are produced by the Scientific Advisory Committee at the RCOG and are up to date reviews of emerging or controversial scientific issues of relevance to obstetrics and gynaecology.
Fetal genetic testing has until recently needed invasive diagnostic procedures (amniocentesis or chorionic villus sampling) carrying a small but significant risk of miscarriage. However since 1997 the presence of cell-free fetal DNA (cffDNA), which comes from the placenta and can be detected from the first trimester of pregnancy onwards, has changed practice and is used for detecting certain conditions.
Obstetricians currently use cffDNA to guide women whose baby is at risk of haemolytic disease of the fetus and newborn (HDFN), a condition where antibodies develop in a pregnant woman’s blood and subsequently destroy the blood cells of the baby she is carrying. It is also used for fetal sex determination in pregnancies at a high risk of sex-linked genetic conditions.
This paper explores the use of cffDNA for chromosome testing and possible sources of error in results from this new technology. It looks at the difference between this technology and current practice and the advantages and disadvantages of cffDNA.
Advantages include the possibility of detecting, without risk to the pregnancy, diseases that may have potentially serious consequences and secondly it is much more accurate than any of the previous screening tests.
However the disadvantage is that pregnant women may occasionally be informed of findings of uncertain significance, such as when there is a discrepancy between the chromosomal makeup of the cells in the placenta and the cells in the baby, known as placental mosaicism. This can result in a healthy pregnancy, however, in some pregnancies it can lead to complications.
The paper also states that due to the high degree of accuracy of NIPT, even early in the pregnancy, it will become easier to find out the sex of the fetus at an early stage. This has a number of socio-ethical implications.
Excellent communication between women and health professionals is therefore essential to understanding the implications of the test results, say the authors.
In conclusion, the paper states that this technology is likely to become a primary screening method for chromosomal abnormalities such as Down syndrome in pregnancy, and that it will enhance the information available to pregnant women while reducing unnecessary invasive procedures.
Professor Peter Soothill, consultant in Fetal Medicine, University Hospitals Bristol NHS Foundation Trust and co-author of the paper said:
“Maternal plasma DNA testing is already being used in the NHS for some conditions and all obstetricians will need to have knowledge of the counselling issues involved and need to take into account the issues around the implications of these test results for women.
“Detection of chromosomal abnormalities such as Down syndrome by this technology will alter the way that prenatal diagnosis and screening is delivered in the UK and in time will give women more information about their pregnancy whilst at the same time greatly reducing the number of invasive procedures.”
Professor Dennis Lo, FRS, Director of the Li Ka Shing Institute of Health Sciences at The Chinese University of Hong Kong, and co-author of the paper said:
“It is very encouraging to see the emerging impact of cell-free fetal DNA analysis for non-invasive prenatal testing. This is a good example of the translation of scientific discovery into clinical practice and heralds an exciting era of genomic medicine.”
Dr Sadaf Ghaem-Maghami, Chair of the RCOG’s Scientific Advisory Committee, added:
“The potential for this technology is exciting and will provide much more accurate results for pregnant women. However, it is important that there are resources and training for health professionals offering this testing and an emphasis on discussions with the pregnant woman before the test about the implications of the results.”
The full SIP paper can be found here.
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The UK National Screening Committee (UK NSC) is currently working with clinicians to trial the use of Non-Invasive Prenatal Testing (NIPT) in the NHS and will make a formal recommendation on whether to introduce the test when the results of the trial are known.
About new RCOG Scientific Impact Papers
RCOG Scientific Impact Papers (formerly SAC Opinion papers) are produced by the Scientific Advisory Committee. They are up to date reviews of emerging or controversial scientific issues of relevance to obstetrics and gynaecology, together with the implications for future practice. These documents have been rebranded to raise awareness of the issues in obstetrics and gynaecology discussed in the documents and to more accurately reflect their content and remit of the Committee.