, released by the Australian Institute of Health and Welfare showed that teenage women had the highest rate of NTD affected pregnancies and women aged 30-34 years the lowest.
'Multiple pregnancies were also more likely to have neural tube defects than singleton pregnancies,' said Dr Samanthi Abeywardana of the Institute's National Perinatal Statistics Unit.
Neural tube defects are major congenital anomalies that result from very early disruption in the development of the brain and spinal cord.
Surviving children are at high risk of frequent illnesses, disability and death.
Spina bifida is the most commonly known neural tube defect.
'During last three decades, mounting evidence has shown that increased intake of folic acid during the period around conception corresponds with a decreased prevalence of neural tube defects,' Dr Abeywardana said.
'In light of this evidence Australia will join many other developed countries in implementing mandatory folic acid fortification of bread making flour (from September 2009) to minimise the births affected with neural tube defects,' she said.
Although there is only about 1 NTD-affected birth per 2000 births, the estimated prevalence of neural tube defects among pregnancies is much higher, at more than 1 per 1000, because some women diagnosed with NTD-affected pregnancies opt for planned termination.
'And, because figures on spontaneous miscarriage due to neural tube defects are not available, the actual prevalence rate among pregnancies is likely to be even higher than this estimated prevalence,' she said.
Although there was no obvious decreasing trend among births in recent years, there was a decrease of over 30 per cent in the neural tube defects prevalence among affected pregnancies between 1992 and 2005.