A report released today by the Australian Institute of Health and Welfare (AIHW) presents information on 33 major birth defects and shows that for many conditions, more males than females were reported to have a congenital anomaly (59% versus 41%).
The report, Congenital anomalies in Australia 2002-2003, shows that the most commonly reported condition is hypospadia (an abnormally-placed urinary opening in the male urethra).
Conditions that affect both sexes, but are more prevalent in boys, include congenital heart diseases, oesophageal defects and kidney cysts.
Chromosomal abnormalities, such as Down syndrome, are the second most commonly reported congenital anomalies.
'For every 10,000 babies born during 2002-2003, about 11 were born with Down syndrome,' said report author Samanthi Abeywardana.
'When terminations of pregnancies were included, the total estimated rate for Down syndrome was just over 26 per 10,000 pregnancies-an increase from previous reports.'
The risk of having a baby with Down syndrome increases with age, from a 1 in 1500 chance for mothers aged 20-24, to a 1 in 184 chance for women 40 and over.
Neural tube defects (such as spina bifida), limb defects, and cleft lip and palate are also covered in the report.
The estimated prevalence of neural tube defects was about 10 per 10,000 pregnancies, about 13% less than the 1998-2001 period.
The rate of anencephaly, the most severe form of neural tube defect, which is always fatal, declined from 5.1 per 10,000 pregnancies in 1998 to 3.8 per 10,000 pregnancies in 2003-a 25% reduction.
'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,' Dr Abeywardana said.
A higher overall rate of congenital anomalies was reported for the births to Indigenous women compared with non-Indigenous women (356 per 10,000 births versus 308 per 10,000 births).
Nearly 72% of the Indigenous women whose pregnancies were affected with a congenital anomaly were aged less than 30 years.
Four states collect and provide data on terminations of pregnancy at less than 20 weeks with a diagnosis of congenital anomaly. Data on terminations due to congenital anomaly is critical in the monitoring the true prevalence of congenital anomalies such as neural tube defects and chromosomal abnormalities.