Liggins Institute research finds pre-term babies and their children at higher risk of becoming overweight
Children born prematurely not only risk becoming overweight adults, but they may also hand a legacy of obesity to their own offspring, warn Auckland medical researchers.
And although early-born males are far more likely than premature females to pile on unhealthy fat in adulthood, world-leading research from the University of Auckland's Liggins Institute has revealed that a second generation of children is at greater risk of being overweight compared to other youngsters.
"So an environmental insult has an impact in the next generation - it has a heritability about it which is quite scary," research leader Associate Professor Paul Hofman told the Weekend Herald.
Professor Hofman was discussing findings by his team which have just been published by the science journal PLOS ONE, after a study of 52 adults in their mid- to late-30s, and 61 of their children, aged from 5 to 10.
Although all the adults were offspring of mothers treated with steroids in a world-famous trial reaching back more than 40 years at Auckland's former National Women's Hospital to improve lung maturity in the womb, 21 began life after normal pregnancy terms, but the other 31 were born prematurely.
Men born prematurely were on average 20kg heavier than their full-term counterparts - weighing in at 109kg versus 89kg - although there was little difference between women of both birth categories.
But children with a prematurely-born parent, regardless of gender, had an average of 12 per cent to 21 per cent more body fat than the offspring of those born full-term.
The study found that 39 per cent of adults in the study born prematurely were obese, compared with just 14 per cent in the full-term category.
Professor Hofman said that although previous studies had alluded to a greater propensity to obesity among prematurely-born adults, the group studied by his team was the oldest to be assessed by the international scientific community.
Earlier studies had shown they were relatively lean as children, although with more fat than would have been expected, but as they reached their 20s they appeared at a slightly increased risk of obesity.
"They seemed to be getting fatter, and now they are in their late 30s we're seeing quite dramatic changes, which haven't been shown before."
"The pre-term women are a little bit fatter, but it's the pre-term men who are markedly fatter - and you've got this hereditary capacity of an environmental insult being transferred to the next generation as well."
Although the Auckland research paper suggests males may have greater capacity to store fat and maintain body weight in response to adverse environments associated with pre-term births, and refers to an overseas study into a possible moderating effect in female rats of the hormone oestrogen, Professor Hofman said the cause of the greater risk of obesity remained speculative.
"If you look at prems in early childhood, they eat bad foods - they have a tendency to eat fewer veges," he said.
"I suspect their food choices and the amount of food they eat are altered by being born earlier, and by being exposed to different sorts of abnormal nutrition when they are young, and that has altered what they wanted as they got older."
But Professor Hofman said that although more than 7 per cent of New Zealanders are born prematurely, they should not despair in a belief that their children and potentially other generations down their bloodline were doomed to become obese.
"What we are seeing is a potential risk of these things," he said.
"It's a preventative thing - we are always a combination of our genes and the environment we are in, and we can modify that environment."
The paper's publication follows a recommendation from a parliamentary committee this week that New Zealand must give higher health-care priority to the origins of life in the womb, and precedes a public forum to be hosted by the Liggins Institute next Friday.