Boys born to overweight women are 40 per cent more likely to grow up infertile, study finds
- Researchers from Denmark studied the fertility and family health of 9,232 adults
- They found that men born to obese women had a higher risk of being infertile
- The same did not appear to apply to the daughters of overweight women
- The team said the causes of the increased risk of male infertility were unclear
- However, such could be related to inflammation or foetal hormone exposure
The sons of women who were overweight prior to giving birth are around 40 per cent more likely to grow up to be infertile, a study has warned.
Researchers from Denmark studied 9,232 adults — of whom around nine per cent were found to suffer from infertility.
The team found an association between mothers who had a body mass index, or 'BMI', of 25 or more in pregnancy and a higher risk of infertility in male children.
The same did not seem to apply, however, to the daughters of overweight women.
Obesity causes a number of changes in the body which can have impacts on a growing foetus — and, in particular, lead to inflammation.
It is believed that hormone disruptions or mineral deficiencies resulting from obesity can also slow an unborn child's development.
In the UK, more than half of all pregnant women are overweight or obese — an issue which increases the risk of miscarriages and stillbirths.
Research has shown that youngsters born to overweight parents are much more likely to become fat themselves — leading to type 2 diabetes and heart disease.
The sons of women who were overweight prior to giving birth are around 40 per cent more likely to grow up to be infertile, a study has warned (stock image)
'Infertility is a global public health issue and it is important that research focus on addressing risk factors,' said paper author and epidemiologist Linn Arendt of Denmark's Aarhus University.
'We know that children born to mothers in the overweight or obesity weight range face higher risks of several adverse outcomes, both in the short and long term.'
Rates of infertility have soared in the past three decades — with an eighth of all couples now finding themselves unable to conceive after a year or longer of trying.
According to experts, a third of cases of inferltity are the result of a man's reproductive issues — and a similar percentage the result of a woman's issues.
The final third of cases are thought to be caused by a combination of both — or are a result of other, unknown, factors.
According to Dr Arendt and her colleagues, the obesity epidemic could be helping to fuel this problem.
'These findings add to evidence that weight during pregnancy may also affect male future reproductive health,' said Dr Arendt.
'Prevention of overweight during pregnancy may be an important tool to preserve fecundity in future generations.'
In the researchers' study, just over nine per cent of participants were infertile — a rate lower than global figures given the age of the subjects, who were in their 30s.
After accounting for potential confounding factors like the mother's age, smoking history and alcohol habits, the team found that sons of women whose BMI had exceeded 25 kg/m2 before pregnancy were 40 per cent more likely to be infertile.
'These findings add to evidence that weight during pregnancy may also affect male future reproductive health,' said Dr Arendt. 'Prevention of overweight during pregnancy may be an important tool to preserve fecundity in future generations' (stock image)
'Maternal overweight could affect the offspring's reproductive health through several potential mechanisms,' explained Dr Arendt.
'Fatty tissue is hormonally active, and foetal exposure to, for example, leptin, androgens and oestrogens has been suggested to interfere with development of the reproductive system.'
This, she said, 'can induce changes which might not manifest until sexual maturity.'
'Some endocrine-disrupting chemicals accumulate in adipose tissue and may become bioavailable and enter the maternal and the foetal bloodstream during remodelling of maternal fat stores during pregnancy.'
'Obesity is also associated with low-grade metabolic inflammation, a proposed factor in programming of reproductive fitness early in life.'
Rates of infertility have soared in the past three decades — with an eighth of all couples now finding themselves unable to conceive after a year or longer of trying. According to experts, a third of cases of inferltity are the result of a man's reproductive issues — and a similar percentage the result of a woman's issues. The final third of cases are thought to be caused by a combination of both — or are a result of other, unknown, factors
Past studies on boys and girls have suggested that there may be a link between maternal overweight and the earlier onset of puberty — as well as other hormonal markers of reproductive health.
In boys, maternal overweight has been found to increase the risk of genital deformities and reduced semen quality.
'To the best of our knowledge, no previous studies have investigated the association between maternal overweight during pregnancy and infertility in their sons or daughters,' said Dr Arendt said.
'This study supports the hypothesis that maternal overweight affects reproductive health in male offspring, but further studies are needed.'
A previous study from the US found that boys — but not girls — born to obese mothers had worse motor skills at the age of three and lower IQ scores at seven.
Obese women are advised to lose weight before becoming pregnant, in the interests of both their own and their baby's health.
However, pregnant women who are obese are not recommended to try to lose weight as this may not be safe, the NHS have warned — and, furthermore, there is no evidence that losing weight while pregnant reduces the chance of complications.
The full findings of the study were published in the journal Acta Obstetricia et Gynecologica Scandinavica.
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