The Health and Disability Commissioner has made an example of a psychiatrist who did not warn a patient that her medication could cause birth defects.
A woman became pregnant while taking Epilim, a medicine used to treat bipolar disorder and seizures.
The drug is known to cause complications at birth and throughout development, but her psychiatrist gave no warning despite her previous child suffering from a postpartum haemorrhage.
Deputy Commissioner Rose Wall found the psychiatrist had breached the Code of Consumers' Rights. She said the incident highlighted the importance of informed consent.
Wall said the investigation also underscored the lack of information surrounding Epilim and other anti-seizure medication.
The patient also received incorrect information from an obstetrician, who told her the drug was safe during pregnancy.
The deputy commissioner recommended that health organisations circulate clearer information about Epilim and similar drugs, particularly for those who plan to have children.
"This case provides an opportunity to ensure information about Epilim and other teratogenic medications is shared widely," Wall said.
"I am pleased to see there has been a concerted effort from multiple organisations to ensure there is clear information available about the risks of Epilim and pregnancy."
The number of pregnant women given Epilim prescriptions has dropped significantly over the past decade - but the job isn't done, she said.
"While this reduction is encouraging, I consider there is still work to be done and I will continue to pay close attention to people's concerns as they raise them," she said.
The woman said her baby is generally well, but suspects his cognition may have been affected by exposure to the drug.