By Eleanor Bradford
BBC Scotland Health Correspondent
Woman often do not begin taking folic acid until they are already pregnant
Women of childbearing age have been urged to take folic acid supplements, even if they are not planning a family.
The Scottish Spina Bifida Association said 15 babies had been born in Scotland with the condition since January - double the normal number.
It said folic acid supplements, which research suggests can prevent many cases, were often taken too late.
Its advice targets all sexually active women of childbearing age because of the numbers of unplanned pregnancies.
Children born with spina bifida are often paralysed from the waist down and can suffer lifelong spinal cord, bowel and bladder problems.
Some children also have brain damage.
Research suggests up to 75% of cases could be prevented by the mother taking folic acid three months before conception, and during pregnancy.
Five-year-old Ella Chambers was diagnosed with spina bifida at birth.
She cannot walk and has hydrocephalus, or water on the brain.
Her mother Melanie said: "I took folic acid tablets as soon as I found out I was pregnant but I've since discovered you need to take it at least three months prior to becoming pregnant.
"I'll never know, if I had taken it earlier, whether I'd be in a different situation now."
The spinal cord develops within the first four weeks of pregnancy so by that stage it's too late
Dr Margo Whiteford
Dr Margo Whiteford, consultant geneticist and chair of the Scottish Spina Bifida Association, said: "This year we've had as many contacts from families in the first half of the year as we'd expect to see for the full year.
"We don't know if this is down to folic acid but we do know that most women don't take enough folic acid at the right time.
"Ladies do know about folic acid preventing spina bifida but they wait until they've missed a period before they start taking it.
"The spinal cord develops within the first four weeks of pregnancy so by that stage it's too late - if the baby's going to have spina bifida it will already have developed it."
It's not known whether the same trend has been seen in other parts of the country, as the latest figures for England, Wales and Northern Ireland date back to 2007.
Five-year-old Ella Chambers and her mother on living with spina bifida
Scotland has the highest rate of children born with spina bifida in the UK because Scottish mothers are less likely to abort the foetus once the condition is diagnosed.
Half of affected pregnancies are terminated in Scotland, compared with 90% in the rest of the UK.
In 2007 the Food Standards Agency (FSA) recommended that folic acid should be added to bread or flour.
However that recommendation is under review following new research which suggested it could increase the risk of colorectal cancer.
The FSA said that anyone who is not about to become pregnant could get enough folic acid from a balanced diet.
However, the FSA adds that pregnant women should take 0.4mg (400 micrograms) of folic acid until the 12th week of pregnancy.
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