TOO MUCH stress can lead to infertility in women, according to the findings of a new study.
High levels of pre-conception stress more than double the chances of a woman failing to get pregnant after 12 months of trying, scientists found.
Meanwhile separate research has found inactive mothers may be preventing their children getting enough exercise by setting a bad example.
Scientists who measured the physical activity levels of mothers and their four-year-old children found a direct association between the two.
An association between high stress levels and a reduced probability of pregnancy had been highlighted in previous research.
The new findings, published in the journal Human Reproduction, involved scientists measuring levels of alpha-amylase, an enzyme in saliva that provides a biological indicator of stress.
Women with high levels of the biomarker were 29 per cent less likely to get pregnant each month than those with low levels. They were also more than twice as likely to be declared infertile.
Study leader Dr Courtney Denning-Johnson Lynch, from Ohio State University in the US, said: “This is now the second study in which we have demonstrated that women with high levels of the stress biomarker salivary alpha-amylase have a lower probability of becoming pregnant, compared to women with low levels of this biomarker.
“For the first time, we’ve shown that this effect is potentially clinically meaningful, as it’s associated with a greater than two-fold increased risk of infertility among these women.”
Dr Lynch urged women having difficulty getting pregnant to consider stress-managing techniques but she pointed out that stress is not the only factor involved in fertility problems and may only play a minor role.
Other research found mother and child activity levels were likely to be linked.
“The more activity a mother did, the more active was her child,” said lead researcher Kathryn Hesketh, from University College London.
“Although it is not possible to tell from this study whether active children were making their mothers run around after them, it is likely that activity in one of the pair influences activity in the other.
“For every minute of moderate-to-vigorous activity a mother engaged in, her child was more likely to engage in 10 per cent more of the same level of activity.
“If a mother was one hour less sedentary per day, her child may have spent 10 minutes less sedentary per day.
“Such small minute-by-minute differences may therefore represent a non-trivial amount of activity over the course of a week, month and year.”
The study included 554 mothers, many of whom worked and had children who attended day-care facilities.
“This approach allowed us to capture accurately both mothers’ and children’s physical activity levels for the whole of the measurement period, matching hour for hour maternal-child activity levels,” said co-author Dr Esher van Sluijs, from the Centre for Diet and Activity Research at Cambridge University.
Just 53 per cent of the mothers taking part in the study engaged in 30 minutes of moderate-to-vigorous activity at least once a week, the results published in the journal Pediatrics showed.
Government health guidelines recommend 150 minutes of “moderate intensity physical activity” such as brisk walking over the course of a week.
New parents are known to be less active than their childless peers.
Once women become mothers their activity levels frequently fail to return to pre-parenthood levels.