Older mothers linked to rise in Down syndrome foetuses

Kate Benson
May 15, 2008

MORE pregnancies produce foetuses with Down syndrome and other chromosomal abnormalities as Australian women wait until their late 30s and 40s to have children, a report says.

The Australian Institute of Health and Welfare's latest report on congenital abnormalities in 2002 and 2003, issued yesterday, found that 2.6 foetuses in every 1000 now has Down syndrome, which causes mental retardation, learning difficulties and physical impairment.

The risk of having a baby with Down syndrome increases with age, from a one in 1500 chance for women aged 20 to 24 to a one in 184 chance for those 40 and over.

One in three babies in Australia is now born to a woman aged over 35, resulting in a surge in the number of pregnancies with abnormalities.

The increase is not resulting in more children being born with Down syndrome, however, as more than 64% of diagnosed babies are aborted or die before birth, the report says.

"The high abortion rate is disappointing but many parents tell us they are pushed into making a decision quickly to proceed or terminate as they are diagnosed and they are not always offered balanced information on Down syndrome," said Jill O'Connor from Down Syndrome NSW.

"We just want people to seek out proper advice before they go down that road."

The report says that other chromosomal defects, such as trisomy 13 and 18, which result in cardiac problems, mental retardation, extra digits and cleft palate, have also risen.

But the rate of spina bifida, where the spinal cord fails to form properly, has dropped thanks to some products, such as bread and milk, being fortified with folate and a continued campaign encouraging women to take folic acid before falling pregnant.

The report says the prevalence of neural tube defects is now about one in 1000 pregnancies, 13% less than in 1998-2001.

"(And) with the introduction of mandatory folate fortification in bread flour in 2009, we expect that the rates of neural tube defects will continue to decline," said the report's author, Samanthi Abeywardana.

About half of all babies diagnosed with spina bifida are terminated.

The most common birth defect is Australia is still hypospadias, where the urethra opens along the penis rather than at the end, with about five boys per 1000 babies born with the condition, which can be corrected with surgery.