This study analysed state-wide data from 1976 to 2013 and showed that in 2013 the numbers of these invasive tests had dropped to their lowest in 25 years, while the number of Down syndrome diagnoses was the highest ever recorded.
This translated to a reduction in the number of invasive tests performed for each diagnosis of a major chromosome abnormality from 100 to six over the 38 year study period. Only 3.4% of pregnant women now have an invasive prenatal test, in contrast to 8.9% at the peak of testing in the late 1990s.
The massive reduction in these invasive procedures in 2013 has coincided with the introduction of the new non-invasive prenatal test (NIPT) for Down syndrome based on cell-free DNA, which is performed via a simple blood test.
“Modern screening tests are now much better at identifying pregnancies at high risk of chromosome defects. Reassuringly, our study shows that this reduction in invasive testing has not been at the expense of detecting affected pregnancies,” said lead researcher, Dr Lisa Hui. “This enormous progress clearly benefits pregnant women by reducing the number exposed to the risks of invasive testing. However, the declining number of tests poses new challenges for the medical profession.”
Co-lead researcher, Professor Jane Halliday said invasive prenatal testing has reached these historic lows due to dramatic improvements in non-invasive Down syndrome screening.
“We observed a steady decline in invasive prenatal diagnosis after the introduction of combined first trimester screening in 2000. The introduction of the new non-invasive screening for Down syndrome in 2013 coincided with an unprecedented annual drop in invasive testing, suggesting a substantial impact of this technology.”
Researchers said projected figures for 2014 suggest invasive testing will drop by a further 25 per cent.
The data were collected from the Victorian Prenatal Diagnosis Database, a unique collaboration between non-profit academic and private commercial laboratories in Victoria (Victorian Clinical Genetics Services, Monash Medical Centre, Healthscope and Melbourne Pathology).