Being born small can have implications for life

Janna MorrisonResearch shows that more than 60% of cardiac disease can be linked to people being born smaller than they should have been. That’s a figure Janna Morrison still finds “pretty startling” despite the reality of it having underpinned her professional life for the past decade.

As a fetal physiologist, and Head of our Early Origins of Adult Health Research Group, (EOAHRG) Associate Professor Morrison leads a team that is investigating why some babies don’t reach their growth potential and the implications of this.

That’s important to know because in humans, unlike in some other animals, a great deal of development occurs before birth.

It’s a complex and challenging field, however, and one still in its infancy in research terms.

For starters, this is not just about the heart. The liver, lungs and other organs are affected by what happens in utero, and none of these changes exist in isolation. And it is not just about the organs themselves, but also the signalling pathways – the molecular mechanisms that underlie growth and the maturation of the organs.

Then there is the broad scope of possible explanations for why a baby’s growth is restricted. It may be preventable factors such as a mother’s poor nutrition or decision to smoke, external factors such as living at altitude, or that something went awry in the womb for no known reason.

“If there is placental insufficiency, for example, then you have less surface area for transfer of nutrients from the maternal to the fetal circulation, so the fetus wouldn’t grow as much,” A/Prof Morrison said.

“But simply by birth weight you don’t know if they were smaller right from the beginning or if something happened later in gestation. You don’t know if something could have been done differently or it was just an event that was out of everyone’s control.”

Knowing that is an important pre-requisite for knowing how, when and if to intervene. But A/Prof Morrison acknowledges that this is not a short-term goal.

“People say to me ‘you guys need to start doing things to make this better’,” she said with a smile. “I say to them ‘this is all pretty new and the answers require long-term intergenerational studies. People have been working to cure cancer for 200 years’.”

For now the priority is to better understand the complex matrix of factors, inputs and implications.

Research in the EOAHRG focuses primarily on the heart, liver, lungs and adrenal gland, with many individual projects under way, often in collaboration with other groups within the Sansom or partners in Australia, North America and Europe.

Current areas of interest are diverse, ranging from improving lung development in small babies, the value of pharmaceutical interventions in the battle against obesity and the role of the periconceptional environment in the timing of birth to the role of the Insulin-like Growth Factor signalling system in heart development and possible links between endothelial progenitor cells and an increased risk of hypertension.

The EOAHRG has a particular interest in the nutritional environment of mothers before conception and during pregnancy, and recently attracted significant publicity for warning that dieting before getting pregnant not only is insufficient to prevent diabetes risks, but could also present new risks.

“It’s an important area because the nutritional environment of the mother determines the availability of nutrients that can go to the fetus,” A/Prof Morrison said.

“If you overnourish the mother there will be more nutrients and changes in hormones, and obviously more glucose, than what the fetus should be exposed to. If you undernourish the mother there will be a decrease in nutrients supplied to the embryo and the fetus. And if the placenta doesn’t develop properly then there will be a decrease in oxygen and nutrients to the fetus.”

While researchers continue to hunt for more clues and specific answers, the broad lessons are there to be learned. A/Prof Morrison believes there needs to be greater understanding of the possible implications of low birth weight, so people can be forewarned and equipped to make sensible lifestyle choices and monitor key health parameters.

“In some countries, such as the UK, there is a greater penetration of knowledge about low birth weight and its implications. There are researchers pushing for policy changes within the UN and WHO to make an early start to life a priority,” she said.

“When we say ‘early start to life’ most people think childhood, but it’s actually before that.”

For more information on the Sansom Institute research activities please visit our webpage.

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