'Shift work and physically demanding jobs linked to lowered fertility'

Feb 09, 2017, 00:16
'Shift work and physically demanding jobs linked to lowered fertility'

The differences were even greater among women working either evening, night or rotating shift patterns. Those with such positions were found to have fewer viable eggs, which can potentially make it harder for a woman to conceive.

As part of the study 473 woman, aged an average of 35, who were undergoing fertility treatment were examined, while another 313 who had completed IVF treatment were also surveyed.

The inverse association between heavy lifting and mature egg yield was stronger among women who were overweight or obese and those aged 37 or older. Yet they do suspect that the fertility issues associated with working non-day shifts may stem from a disruption in a woman's circadian rhythm.

However, Minguez-Alarcon admitted that some of those women might be exposed to some other environmental factors that could affect their "egg quality".

"We need further large studies to confirm these findings before we can advise women if their night shifts have a potential negative impact on their egg quality and IVF outcome".

In addition, compared with those whose jobs did not entail heavy lifting, women going through IVF with physically demanding jobs had a lower total reserve of eggs and fewer mature eggs - reductions of almost 9% and almost 14.5%, respectively.

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For instance, it could be that the amount and type of work a women does could be related to other aspects of her life, such as socioeconomic status, that made her less fertile.

The findings were discussed February 7 in the journal Occupational and Environmental Medicine.

"We're not entirely sure of the biological mechanisms that are underlying this but it seems that physically demanding work on top of an obesogenic or overweight environment are two combined stressors that seem to be really detrimental to a woman's ability to get pregnant", said co-author Audrey Gaskins, research associate at the School of Public Health. "As women with fewer mature oocytes [eggs] would have fewer eggs which are capable of developing into healthy embryos".

The authors caution that the study is observational, so no firm conclusions can be drawn about cause and effect.

"It is hard to hypothesise a mechanism by which a physically demanding job may have a negative effect on ovarian reserve, as the number of eggs (oocytes) is determined at birth and lost progressively throughout life, with smoking having been shown to be the main toxin that significantly diminishes ovarian reserve". The study focused on women who have physically demanding jobs in order to see if their fertility is affected by their jobs. Another factor that can affect fertility is obesity.

About 40 per cent of women said they had to regularly move or lift heavy objects, while a fifth said their jobs were moderately to very physically demanding.