Health experts say pregnant women who take medication for epilepsy need to speak to their doctor.
Anti-epileptic medication has been blamed for congenital malformation and learning problems in children whose mothers took the medicine while pregnant.
Denise Astill took anti-epileptic medication while pregnant following advice she says she was given by specialists.
"I actually consulted two specialists prior to getting pregnant and asked specifically what sodium valproate would do to an unborn baby," says Ms Astill.
The Auckland mother says she was told it could cause spina bifida or neural tube defects but if she took folic acid with her medication she would be okay.
"The other option was that I could come off the medication but I would have seizures, therefore the baby would be oxygen deprived and brain damaged," she says.
Not wanting to take the risk, when Ms Astill got pregnant she still took her anti-epileptic medication.
Her twin girls were diagnosed with Feotal Valproate Syndrome.
"We just noticed things happening one after another after another. It wasn't until they were four and a half years old that they were officially diagnosed," she said.
"They do have learning difficulties, there is cognitive issues. There's speech language issues and anxiety is huge for our kids and this has led to a lot of heartbreak actually."
Ms Astill has since started the Foetal Anti-Convulsant Syndrome New Zealand (FACS NZ) group.
The group has teamed up with Auckland DHB and ACC to launch an awareness campaign highlighting the issue.
They say the campaign focuses on the importance of women talking to their doctor about the pros and cons of taking anti-epileptic medicine during pregnancy.
Not all women who take the medication will have problems.
Starship paediatric neurologist Dr Rakesh Patel says it's a balancing act.
"These drugs have been implicated in causing learning difficulties as well as anatomical differences," said Dr Patel.
But he says medication plays a crucial role in controlling epilepsy.
"These medications represent a very important part of their lives. They give them independence. There are an increasing number of alternatives that work as well and there are lifestyle changes that may need to be made," he said.
It's understood more than 28,000 Kiwi women of childbearing age took anti-epileptic medication last year.
"We need to drive home the critical message that women who take anti-convulsant medication need to discuss the risks and benefits with their doctor, even if they aren't actively planning on getting pregnant," said ACC's chief clinical advisor, Dr Peter Robinson.