Stricter policy for a drug used to treat epilepsy and bipolar disorder has been rolled out by Medsafe, due to its tendency to cause serious birth defects.
Sodium valproate, also known as Epilim, is now only available as a last resort for women of childbearing age.
Data from global biopharmaceutical company Sanofi shows that in the general population around 2 in100 babies will be born with birth defects.
That number goes up to 10 in100 if the mother is taking Valproate. Spina bifidia, cleft palates, and defects with vital organs such as the heart and kidneys are some of the issues the drug can cause.
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An even higher number of babies are likely to have developmental issues.
Nearly half of every 100 babies born to mothers using Valproate will experience lower intelligence, delayed speech and walking, memory issues and other disorders, such as autism and ADHD.
This week Medsafe imposed stricter restrictions on the drug - it can now only be used by women of childbearing age if all other treatments are ineffective.
It must also be initiated and supervised by a specialist.
Despite this change in policy, Foetal-Anti-Convulsant Syndrome NZ executive officer Denise Anstill says it's not enough.
She believes the changes need to be legislated and made mandatory.
Ms Anstill has two daughters aged 17 who both have Foetal-Anti-Convulsant Syndrome (FACS).
FACS is a combination of three individual syndromes, where different anti-epilepsy drugs have crossed the placenta and entered the foetus, causing defects. The other two drugs that can cause the syndrome are Carbamazepine and Hydantoin.
Although her daughters don't have spina bifida, they do have a host of other issues, including cognitive issues, epilepsy, obsessive compulsive disorder, and behavioural issues.
They also have issues with their eyesight, their bowels, and their hearts.
"We don't know what the future holds for them," Ms Anstill told NZME "We do know that to live independently they are going to need to be assisted and supported for the rest of their lives."