Growth restricted babies and asphyxia – cardiovascular impacts

Hudson Institute

The health effects of fetal growth restriction (FGR) can last a lifetime and the latest research from Hudson Institute is showing just how pervasive those effects can be on the cardiovascular system.

In two major studies researchers have found that

  1. Being growth restricted in the womb increases the risk of future cardiovascular disease (CVD) with changes in the cardiovascular system that can be detected even as early as days to weeks after birth, even if the usual measures of cardiovascular health might not indicate it,
  2. The cardiovascular impacts from birth asphyxia could be even more damaging on babies born growth restricted.
Charmaine Rock and Dr Beth Allison in the lab outlining their research on growth restricted babies at Hudson Institiute
L-R: Charmaine Rock and Dr Beth Allison

Recent research by Dr Beth Allison and her team, published in the American Journal of Physiology-Heart and Circulatory Physiology, showed that an increased risk of future cardiovascular disease may be set even before growth restricted infants are born.

PhD student, Charmaine Rock said this means a new approach is needed to monitoring the ongoing health of people born with FGR.

“We compared lambs born with FGR to fully-developed lambs and found that those with FGR had rounder hearts, which can affect the way the heart functions and ability for their blood vessels to dilate, which can change delivery of blood to the organs,” she said.

Therapeutic intervention warranted for growth restricted newborns

“What was really interesting was that we could detect these changes at the cellular level when the usual measures of cardiovascular disease showed nothing out of the ordinary.

“Further investigation revealed impairment to one of key pathways that drive the ability of the blood vessels to function – the prostanoid pathway. This is a really exciting finding because our work provides new insights that may warrant new therapeutic interventions to improve cardiovascular development in growth restricted newborns.”

What is the impact of birth asphyxia on growth restriction?

The Hudson Institute of Medical Research team also examined whether exposure to perinatal asphyxia presented greater risks to those born growth restricted than those who were not.

The results were good and bad.

“Contrary to our hypothesis, we found that those born growth restricted maintained blood flow to the brain for longer and needed fewer chest compressions during resuscitation,” Dr Allison said.

“This suggests that preterm growth-restricted infants may be physiologically more resilient to perinatal asphyxia than other infants.”

“However, we also found that during recovery from asphyxia there was an overshoot in blood flow to the brain which may increase the risk of brain damage in those born growth-restricted and preterm.”

This pre-clinical study showed for the first time that being born growth restricted impacts your response to a second insult – in this case asphyxia.

Dr Allison believes the outcomes of this study have resulted in more questions.

Antenatal care of growth restricted babies deserves investigation

“Firstly, does the different response to asphyxia protect growth restricted infants? We now know they are likely to maintain blood flow to the brain for longer – and also show a greater increase in blood flow to the brain after birth – but we remain unclear as to whether this protects the brain from damage.

“Second, we clearly show that growth restriction leads to a different response to asphyxia. So, does that make it more likely that doctors will fail to notice this serious and potentially life-threatening event in growth restricted babies?”

Dr Allison believes her research focusses attention on the special care that our smallest babies – those born growth restricted – need in their first days and weeks.

“This research is the first to show the impact of asphyxia on the cardiovascular hemodynamic changes that occur in growth restriction,” she said. “It is clear that this area of antenatal care deserves more investigation.”

FGR facts

  • Fetal growth restriction affects up to 18,000 Australian babies per year
  • Being born growth restricted increases the risk of morbidity or perinatal mortalities up to 20-fold at all gestational ages compared to infants who are appropriately grown
  • Growth restricted newborns often require significant medical intervention after birth which further exacerbates pathophysiology and increases hospital stay.

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