A new treatment which could prevent up to 6000 New Zealand babies being born prematurely has been proven safe.

About 5-10 per cent of babies are affected by fetal growth syndrome – between 3000 and 6000 in New Zealand or 25 million globally each year.

The condition was usually linked to problems with the placenta which meant the foetus did not get enough nutrients and oxygen and often resulted in the babies having to be induced prematurely.

Babies born premature carried a greater risk of problems with growth, learning, and adult diseases such as obesity and diabetes while babies who did not grow properly in utero were also more at risk of being stillborn or dying shortly after birth.

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But findings from a team of researchers from Auckland University's Liggins Institute and the University of Otago, published in the Journal of Physiology today, could pave the way for a new, safe treatment.

They injected pregnant sheep with the condition with a growth drug and found that, not only did the drug boost growth in late pregnancy, it had no negative effects on survival rates or health and development in the two weeks following birth.

The drug, insulin-like growth factor-1, had been previously proven to improve fetal growth in mammals but this was the first study to look at its effects during and after birth.

Study leader and director of the Liggins Institute Frank Bloomfield said it was an important result which could lead to trials in at-risk pregnant women.

"There was a risk that the placenta would be unable to meet the increased demands of the larger foetus during periods of stress, such as labour, so our findings are reassuring," he said.

"A treatment that improved growth, presumably through improving placental function as the animals do not show any signs of getting more compromised, would mean that growth-restricted babies may be able to stay in the womb longer. This could be a very important factor for improving long-term outcome, as it is preterm delivery that is the major problem for these babies."

During the study researchers also discovered a placental hormone in the mother's blood which could help detect fetal growth restriction more accurately and less invasively.

The hormone was linked to the levels of oxygen received by the foetus which was a key indicator of fetal wellbeing and size.

Currently, oxygen levels could be measured only by methods that put the foetus at risk and, at most, only half of the cases of fetal growth restriction were picked up in utero. Health professionals generally relied on routine measurements of the mother's belly to identify growth issues and then used ultrasound to get a measure of the fetal wellbeing.

"A blood test that could detect a biomarker for fetal well-being would be a huge benefit – simple, non-invasive, quick and inexpensive," said Bloomfield, who is also a neonatologist at Auckland's National Women's Health.