A New Zealand study has found repeat doses of steroids given to premature babies before birth is safe.

The Auckland University study has established it won't affect the long-term development of these babies.

Researcher at the Liggins Institute Dr Chris McKinlay says with few treatments available for mothers at risk of preterm birth, this is an important finding .

He says many doctors were reluctant to use this promising treatment because of concern that exposing babies to steroids would increase the risk of long-term complications like diabetes and heart disease.