Babies born late preterm at 35 weeks could be at higher risk of cardiovascular disease in adult life than those born at full term, according to new research by Hudson Institute of Medical Research scientists.
The scientists found that being born late preterm (35 – 36 weeks gestation) was linked to a decrease in regulation by the parts of our nervous system that work together to keep the heart rate under subconscious control – a key marker of heart disease.
“This study suggests that it is not only babies born extremely or very preterm (earlier than 32 weeks) that may be at greater risk of developing heart disease later in life,” Dr Beth Allison, a Senior Researcher in The Ritchie Centre, Hudson Institute and Monash University, said.
“Infants born late preterm are generally considered to be at a very low risk for long-term health problems in adulthood or mortality after birth. However, this study gives us some clues as to how preterm infants could be at an increased risk of heart disease in adulthood.”
The findings of the preclinical study have been published in the journal Experimental Physiology. Using preclinical models that mimic the effects of babies born at 35 weeks’ gestation, the researchers tracked metabolic and heart function from birth to early adulthood.
Male and female differences
They looked at the effects of the sympathetic and parasympathetic nervous systems, which work together to stabilise blood pressure, on the peaks and troughs of blood flow waveforms.
Key differences between males and females were discovered. In young adult females that were born late preterm, the sympathetic nervous system (which increases heart rate) was less activated, an early marker of cardiovascular disease.
In males, the results were different. Adult males born premature lacked the innate reflexes of the nervous system that control heart rate. This could mean that men who were born premature may be unable to regulate blood pressure within normal limits, an early sign of an increased risk of cardiovascular disease.
Preterm is defined as babies born alive before 37 weeks of pregnancy are completed.
The World Health Organisation’s sub-categories of preterm birth, based on gestational age are
Extremely preterm (<28 weeks)
Very preterm (28 to <32 weeks)
Moderate to late preterm (32 to <37 weeks)
Growing understanding of preterm risk
One limitation is that betamethasone, a drug given to preterm babies to quickly mature their lungs and which can have dramatic effects on cardiovascular function, was given to the preterm group and may affect the results.
Despite this limitation, Dr Allison says the new research adds to a growing body of evidence that is helping to understand the mechanisms leading to hypertension, stroke and cardiovascular disease in adults born both preterm and normal term.
“Preterm babies make a rapid transition to the world outside the womb at a time when their organs and autonomic nervous system are not yet matured or fully prepared. We are only beginning to understand the effects that this may have later in life,” she says.
“More and more babies are surviving preterm birth. It’s vital to better understand the effects of changes that are occurring in the bodies of preterm infants – even those born only a few weeks premature – on long-term development, in order to minimise health problems throughout their lives.”
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