Victoria has achieved historically low rates of prenatal diagnostic testing due to advances in screening for chromosome conditions, according to new data from the Murdoch Children's Research Institute.

The Annual Report on Prenatal Diagnostic Testing, 2020, produced by the Reproductive Epidemiology Group at Murdoch Children's, reported that only one in 50 pregnant women had a prenatal diagnostic procedure to detect fetal abnormalities, down from one in 10 pregnant women 20 years ago.

Murdoch Children's researchers Professor Jane Halliday, Associate Professor Lisa Hui and Cecilia Pynaker wrote the report, using the Victorian Prenatal Diagnosis Database (VPDD).

Pregnant women in Australia are offered voluntary prenatal screening to identify changes in the baby's chromosomes (packages of DNA) that lead to conditions such as Down syndrome or Edward syndrome. Each year, the VPDD collects data on diagnostic testing to monitor changes in clinical practice and prenatal detection of chromosome conditions.

"Two decades ago, the most common reason for women to have a diagnostic test was because of advanced maternal age," Associate Professor Hui said.

"Up to one in 10 women had a procedure during pregnancy, which could be followed by pregnancy loss, or bleeding."

Today, the most common reasons to have the diagnostic invasive test are an ultrasound abnormality or a positive non-invasive prenatal testing (NIPT) screening result and only one in 50 women now have this procedure during pregnancy.

"This dramatic decline in invasive testing is due to improvements in screening for pregnancies with an increased chance of Down syndrome or other chromosome conditions," Associate Professor Hui said. "We have fewer false alarms with our screening tests now while maintaining a high detection rate."

Diagnostic testing can also be done for rare single-gene conditions due to advances in understanding the genetic causes of rare childhood diseases. The VPDD is a long-standing collaboration between the MCRI Reproductive Epidemiology Group, the Victorian Clinical Genetics Services (VCGS) and Monash Pathology.