It's one of the most devastating outcomes in any pregnancy: a baby growing inside its mother suddenly — and often inexplicably — dies.

Key points: The Hunter Medical Research Institute says most stillbirths are triggered by an ageing placenta

The Hunter Medical Research Institute says most stillbirths are triggered by an ageing placenta HMRI hopes to develop a blood test for stillbirth risk in three to five years

HMRI hopes to develop a blood test for stillbirth risk in three to five years One in 100 Australian pregnancies that reaches 20 weeks gestation ends in stillbirth

Almost one in 100 pregnancies in Australia will end with the death of the baby.

But an Australian researcher has had a major breakthrough in understanding the mysteries of stillbirth, and is developing a test which could alert obstetricians when a baby is in grave danger.

"It certainly is the most exciting project I've been involved in so far, with the potential to influence people's lives around the planet," Professor Roger Smith AM said.

Professor Smith's team at the Hunter Medical Research Institute (HMRI) has found that many stillbirths are triggered by a deteriorating placenta.

"As you look around at everybody you know, you'll notice that different people age at different rates," he said.

"And it's almost certainly the same with the placenta. Some placentas age more rapidly than others."

Monitoring the placenta could save babies

The placenta is a vital organ which connects a growing baby to its mother via the umbilical cord.

Professor Smith believes some placentas begin to age weeks before the mother's due date, slowly starving the foetus of the nutrients and oxygen it needs to survive.

"If the placenta is not working, the levels of oxygen fall in the baby, and if they get low enough, the baby will die," Professor Smith said.

A placenta that is deteriorating emits an enzyme called aldehyde oxidase.

Professor Roger Smith (left) and his colleagues Kaushik Maiti (centre) and Zakia Sultana are developing a test for stillbirth risk ( ABC News: Rebecca Armitage )

Professor Smith hopes to develop a test within the next three to five years that will alert doctors to elevated enzyme levels in a mother's bloodstream.

"It's possible that we'll be able to develop diagnostic tests to pick up in the mother's blood the signs of ageing of the placenta, and therefore predict this devastating event, so that the obstetricians can perform a caesarean section and get the baby out before the baby dies," he said.

However, a baby only has a good chance of surviving outside the womb after 27 weeks gestation.

"If a baby is too early in pregnancy to be delivered, we may be able to give drugs that inhibit that enzyme to slow the ageing of the placenta, and allow the baby to stay in the uterus until it is likely to survive when it's born," Professor Smith said.

Placenta research could eventually extend human life

Professor Roger Smith says healthy placenta cells are damaged by the enzyme, aldehyde oxidase ( Supplied: Hunter Medical Research Institute )

The enzyme aldehyde oxidase is responsible for signs of ageing in the human body, including the placenta.

If Professor Smith's research team can figure out a way to control its presence in the body, the medical possibilities could be endless.

"It's possible that if we develop different ways of stopping this enzyme working to cause damage, it may lead to lower levels of ageing in other tissues and perhaps even healthy life extension," Professor Smith said.

However, Professor Smith's immediate priority is reducing the number of stillbirths in Australia.

"I think it's really important for mums of stillborn babies to understand that it's not their fault," he said.

"This is something that's happened to the placenta, they had very little or no control over it.

"There was nothing they could do to prevent it. So they shouldn't feel guilt about it."

His research is published online in the American Journal of Obstetrics and Gynaecology.