‘Too posh to push’ mums who choose to give birth by caesarean may be putting their babies at risk of obesity and diabetes later in life, suggests new research.
The study shows babies delivered just two weeks early are more likely to develop diabetes and become obese when they grow up.
It also means they are at greater risk of dying before their time because of other illnesses triggered by the conditions, according to the research.
Scientists warned elective caesarean sections being carried out too soon may be endangering children.
The health prospects of slightly premature infants have traditionally been regarded as similar to those that arrive on time.
But the latest findings, published in the American Journal of Obstetrics and Gynecology, add to growing evidence this is not the case.
There are more than 125,000 babies born ‘early term’, at 37 to 38 weeks, just in England, each year. They usually look as healthy as their full term counterparts born at 39 to 41 weeks.
But one of the largest studies of its kind that followed the health of 225,000 children up to the age of 18 found many are not.
They are more prone to problems with the metabolic and hormonal, or endocrine, systems that can lead to diabetes and a host of other illnesses.
Professor Eyal Sheiner, of Ben-Gurion University of the Negev in Israel, said: ‘We found hospitalisations up to the age of 18 involving endocrine and metabolic morbidity were found to be more common in the early term group as compared with the full term group, especially at ages five and older.’
She added: ‘Obesity was significantly more frequent among the early term.’
Her researchers also discovered children older than five had much higher rates of type I diabetes when born early term. This is the form that develops in childhood and is not linked to lifestyle factors.
They said these conditions may increase the risk other associated illnesses with a long term impact on health and wellbeing. This leads to increased healthcare expenditures and a shorter lifespan.
Prof Sheiner, who is also head of the obstetrics and gynaecology department at Soroka University, Beersheba, said babies born between 39 and 41 weeks of gestation have better outcomes than those born either before or afterwards.
Her results were based on an analysis of 54,073 early term deliveries that were compared with 171,000 full term ones.
Prof Sheiner added: ‘Pregnancies ending at early term were more likely to be complicated by hypertensive disorders and maternal diabetes - both gestational and pre-gestational.
‘Deliveries were more often caesarean, and mean birthweight was significantly smaller.
‘Babies delivered at early term were also more likely to be low birthweight - less than 5.5 pounds (2.5 kilograms).’
In the UK about a quarter of births now happen by caesarian section. Previous research has suggested in some hospitals more than half of those who have the operation have it before the 39th week, in contravention of official NHS guidelines.
Five years ago a study of 14,000 British children found early term babies were 10 per cent more likely to suffer from a long standing illness, or asthma and wheezing, than full term ones.
They were also 40 per cent more likely to have been prescribed an asthma inhaler at the age of five.
Experts have pointed out research and resources are frequently directed towards very premature babies, who have the highest risk of death and health problems.
But their numbers are comparatively small, with about 8,000 born each year in England.
It is being increasingly appreciated babies born even a few weeks early can have long term health and behavioural issues.
There are a number of things pregnant women can do to reduce the risk of giving birth early including maintaining a healthy weight, staying active and avoiding stress, smoking and infections.