The dramatic success of noninvasive prenatal testing (NIPT) using cell-free DNA in maternal blood has widespread medical and ethical implications.
Advances in genomic prenatal testing
Our genetic material, or DNA, is organised into 46 packages called chromosomes. Large changes that cause gains or losses of chromosomes are referred to as chromosomal conditions. Every baby has a small chance of being born with a chromosomal condition, the most common of which is Down syndrome.
The aim of prenatal screening is to offer a safe, accessible test to identify women at increased chance of having a baby with a chromosome condition. Prenatal screening for Down syndrome has been an established part of antenatal care for several decades. Women who are identified as 'high risk' by a screening test are then offered an invasive diagnostic test, such as amniocentesis, for confirmation. However, all diagnostic tests carry a small risk of miscarriage and their use must be considered carefully.
How have advances in genetic testing benefited pregnant women?
Our concept of genetic testing has advanced dramatically since it was discovered that DNA fragments from placenta are detectable in the pregnant woman's blood. We are now able utilize this uniquely accessible genetic material from the placenta to check the health of the developing fetus with a simple blood test, so called 'noninvasive prenatal testing' (NIPT).
Compared with traditional screening tests, NIPT detects Down syndrome and other chromosome abnormalities with unprecedented accuracy. This has brought great benefits to pregnant women, with fewer women undergoing unnecessary invasive prenatal tests due to erroneous 'high-risk' screening results. However, NIPT is expensive and must be fully funded by the woman, creating enormous barriers to access.
Are there wider consequences of this progress in noninvasive prenatal testing?
There many important medical, ethical and workforce implications of the revolutionary technology underlying NIPT. This include the expanding range of genetic conditions detectable by NIPT, incidental diagnosis of maternal conditions, the impact of declining invasive procedures on specialist procedural skills, the changing role of the 11-13 week nuchal translucency ultrasound, and the ethical issue of unequal access to NIPT.
The unexpected diagnosis of maternal malignancy is a rare but well-recognised consequence of widespread testing with NIPT. We recently collaborated with colleagues at the West Australian Gynaecological Oncology Biobank and the Victorian Clinical Genetics Service to investigate the use of NIPT for the noninvasive detection of tumour DNA in the blood of nonpregnant women with ovarian cancer.
How can we assess the wider impact of NIPT in Victoria?
We have partnered with the Reproductive Epidemiology group lead by Professor Jane Halliday at the Murdoch Childrens Research Institute to study the rapidly changing environment of prenatal testing in the Perinatal Record Linkage (PeRL) study. By analysing data from the four Victorian cytogenetics laboratories, the central serum screening laboratory at the Victorian Clinical Genetics Service, and various private ultrasound practices we hope to map the complex prenatal screening pathways currently being negotiated by pregnant women in Victoria. We are also investigating the relationship between socioeconomic disadvantage and the utilization of various prenatal screening tests in order to determine if financial barriers are influencing rates of invasive prenatal testing among Victorian women.
We gratefully acknowledge the support of our funders for this research theme, including the NHRMC, the Norman Beischer Medical Research Foundation and Mercy Health.