New Zealand has the third highest rate of prescription opioid use, during pregnancy

A new Otago University study with 13 high income countries has found eight per cent of New Zealand pregnancies are exposed to opioids.

The painkillers increase risks of adverse effects such as defects, pre-term births and neuro-developmental conditions.

Otago University lecturer, Dr Sarah Donald says although this is unexpected, it isn't as scary as it sounds.

She says of the opioids being dispensed in New Zealand, it was predominantly codeine which has fewer health impacts than stronger painkillers.