Working shifts can hamper a woman’s ability to conceive , a study has found.
Shift work, evening work or working outside the usual nine to five day significantly reduces a woman’s ability to start a family, according to the research published in journal Occupational & Environmental Medicine.
Previous research has linked occupational factors to the ability to carry a pregnancy to term.
But this is the world’s first study to assess whether workplace factors affect a woman’s biological capacity to have a baby .
US researchers at Harvard University looked at indicators of ovarian reserve - the number of remaining eggs and levels of follicle stimulating hormone (FSH) - in 500 women.
These indicators rise as a woman ages and signal dwindling fertility. They also looked at ovarian response - the number of mature eggs capable of developing into a healthy embryo.
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Women working during the evening, doing night work, or on rotating shifts had fewer mature eggs, on average, than those working within normal working hours.
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And the difference was even greater among those specifically working evening and night shifts, possibly because of disruption to the body clock, suggest the researchers.
The study also found a link between women who had physically demanding jobs and lower fertility levels.
Dr Lidia Minguez-Alarcón, of the Harvard TH Chan School of Public Health, said: “These findings have clinical implications, as women with fewer mature oocytes would have fewer eggs which are capable of developing into healthy embryos.”
She added that the results “suggest that occupational factors may be more specifically affecting oocyte production and quality, rather than accelerating ovarian ageing.”
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She cautioned that this was an observational study, so no firm conclusions can be drawn about cause and effect.
Prof Darren Griffin, Professor of Genetics at the University of Kent, said: “The key message of this paper is that women who undertake heavy lifting or work unsociable shift hours produce significantly less mature eggs.
“It seems that the effect is more exaggerated with increased age and body mass index. The authors measured a number of occupational factors but these were the only ones that showed marked results.
“Women who are trying to start a family may wish to take the study into account, perhaps avoiding heavy lifting and unsociable work hours as much as is possible during this time, especially if they are not falling pregnant within the first year of trying.”
Prof Alastair Sutcliffe, Professor of Paediatrics at UCL, added: “Human beings like light. When sunlight hits our retinae, the serotonin ‘happy hormone’ goes up instantly in the brain.
“Hence we love sunny winter days, but not dank overcast ones. So shift work is not a biologically good way to work and folks who have to do this are known to get many ill health risks such as hypertension.
“So what does this study mean? If trying to optimise fertility, stick to the day job and leave the lifting to their partner.”
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