Results from a landmark University of Otago Christchurch – Ōtākou Whakaihu Waka Ōtautahi longitudinal study of New Zealand babies shows premature birth has few significant effects on long-term health for most – although several challenges remain.
The New Zealand Very Low Birthweight (VLBW) Study has followed the health and progress of all babies born in Aotearoa in 1986 weighing less than 1500 grams, comparing their health and progress with a cohort of same-aged peers over three decades.
The study is one of only two national longitudinal studies of VLBW infants born in the 1980s, the other being from the Netherlands, which lacked a comparison group.
Today's New Zealand Medical Journal has now published an overview of data from 30 studies from 2013 to 2016, when the cohort of 250 VLBW babies were aged 28 years. Of the cohort, 82 per cent were born very preterm (at less than 32 weeks gestation, between 8 and 16 weeks premature).
The overview shows most were thriving in their third decade of life.
Emeritus Professor Brian Darlow
"Very low birthweight babies take up a large proportion of resources in our Neonatal Intensive Care Units, but as they grow, they hold their own, which is very positive news," says the University of Otago, Christchurch's Emeritus Professor Brian Darlow, who has led the study since its inception.
"Despite their more challenging start in life, when last tested, the majority of VLBW adults were generally living healthy, productive lives similar to babies born at the same time and at a healthy weight, with the cohort's mean values for nearly everything we measure within the normal range for age."
However, while reassuring, Professor Darlow says the results do point to some challenges and concerns for the long-term health of the two per cent of New Zealand babies born very premature.
"We constructed a score of biomedical measurements that are known to change with age and which suggest VLBW adults, on average, have a more advanced "physiological age" towards the end of their third decade than term-born controls. As such, they may be more vulnerable to early organ decline and future health issues," Professor Darlow explains.
"Very preterm birth is a lifetime condition and extra medical surveillance is warranted, particularly for blood pressure, heart, lung, and kidney function as well as blood sugar control."
This overview study concluded that compared with their term-born peers, VLBW adults at age 28 had higher systolic blood pressure, slightly smaller, stiffer hearts and more visual impairment. They also experienced slightly poorer lung function and tended to exercise less often and less vigorously than controls. They were also on average 5cm shorter and lighter (but with little difference in Body Mass Index).
Extensive testing also showed there was a gap of 9.4 points in adjusted mean IQ between VLBW adults and controls, and some differences in tertiary education levels, employment, welfare dependence, and self-perceived executive functioning.
VLBW adults self-reported similar levels of self-esteem as their peers, but slightly poorer Quality of Life scores, mostly related to physical and health issues. They had also experienced more mental health problems than term-born controls - although this difference was small.
Dr Sarah Harris
As a result of these findings, Professor Darlow and the new study leader, University of Otago Senior Lecturer and paediatrician Dr Sarah Harris, say it's vitally important the study is continued, to assess the impact of premature birth on adults as they age.
"We plan to apply for funding to continue the study, to test if subsequent physiological ageing of our very low birthweight cohort will remain at the same pace as others or be possibly accelerated," Dr Harris explains.
"We have a unique opportunity to study this and build on the tremendous contribution by study participants to our understanding of the long-term impact of premature birth on health and well-being.
"We know that accelerated ageing brings with it the risk of earlier chronic disease, with a suggestion also that babies born very premature may develop hypertension, heart disease, and lung problems earlier. These factors make it vitally important we complete further assessment as they age."
Both authors stress that in light of the overview study's findings, all very prematurely born babies should be seen regularly by their GP or health provider.
"Routine general practice visits provide an opportunity to check for any relevant symptoms, and we recommend basic health surveillance such as spirometry, blood pressure, and blood glucose checks through childhood and adolescence, as well as earlier screening for cardiovascular disease in adulthood," Professor Darlow says.
"As in the general population, for a child born with a very low birthweight, adopting a healthy lifestyle, not smoking, having annual influenza immunisations, following a healthy diet, and taking regular exercise are the cornerstones to remaining fit and well."
