- A woman's ability to conceive maybe
affected by the type of work, as well as the shift patterns.
- Physically demanding jobs and shift
outside normal working hours reduced the quality of eggs.
- It also lowered the
number of remaining eggs in women compared to women whose work was not physically demanding.
A physically demanding job or work
schedule outside of normal office hours may lower a
woman's ability to conceive.
The findings also showed that the quality
of eggs were reduced by heavy lifting at work and evening, night or rotating shift
‘Women who reported lifting or moving heavy objects at work had fewer total eggs, fewer mature eggs and fewer number of remaining eggs compared with women who reported never lifting or moving heavy objects at work.’
Previous studies that have linked
occupational factors to fertility
have measured in outcomes, such as, time of pregnancy and the
ability to carry a pregnancy to full
But this is the first study to assess
that a woman's biological capacity to have a baby may be influenced by
study involved 473 women attending one fertility clinic, whose
average age of the women was 35, while their average BMI was 23.
They analyzed indicators of:
- Ovarian reserve - which represents the number of
remaining eggs (antral follicle count)
- Levels of follicle
stimulating hormone (FSH) -
which rise as a woman ages and represent dwindling fertility
- Ovarian response - which are the number of
mature eggs capable of developing into a healthy embryo in 313 of the
women who had completed at least one cycle of IVF by December 2015
These women were all part of an ongoing
(EARTH) study, which has been looking at environmental and dietary factors that
might affect fertility since 2004.
The women were quizzed about the level of
physical exertion required for their job and the hours and patterns worked, as
well as leisure time physical and sedentary activities.
The results showed that:
- 4 in 10 (40%) women said
that their job required them to regularly move/lift heavy objects
- 1 in 4 (22%) said that
their jobs were moderately to very physically demanding
- 9 in 10 (91%) said
they worked during normal office hours
Ultrasound revealed that:
- The ovarian reserve or
the number of remaining eggs ranged from 8 to 17 among all 473 women
- The average number of
mature eggs retrieved from the 313 undergoing an IVF cycle was 9
Physically demanding jobs lowered the
number of remaining eggs in women compared to women whose work did not require
heavy lifting. But it did not seem to make any difference to FSH levels.
Physically demanding jobs reduced the
total number of remaining eggs by 9% and number of mature eggs by nearly 14.5%
in women who were undergoing IVF.
Women working evening, night or rotating shifts had
fewer mature eggs, on average, than those working normal shifts. This could be
as a result of disruption to the body clock.
Overweight women (BMI of 25 and above) who had physically
demanding jobs also had fewer mature eggs compared to those women if similar weight
who did not have a physically demanding job
Older women (37 and above) also had only
fewer mature eggs compared to younger women.
"These findings have clinical
implications, as women with fewer mature oocytes would have fewer eggs which
are capable of developing into healthy embryos," explain the researchers,
who go on to add that the results "suggest that occupational factors may
be more specifically affecting oocyte production and quality, rather than
accelerating ovarian aging."
Being an observational study, no firm
conclusions can be drawn on the causal relationship. Moreover, the researchers were
unable to assess the impact of other potentially influential factors, such as
long working hours or switching between day and night shifts.
"Taken together with our results, it
appears that lower oocyte quality could be one pathway mediating the
relationship between high frequency of moving or lifting heavy loads at work
and reduced fecundity," the researchers suggest.
The research is published online in
Occupational & Environmental Medicine
- Lidia Mínguez-Alarcón et al. Occupational factors and markers of ovarian reserve and response among women at a fertility centre. Occupational & Environmental Medicine; (2017) doi.org/10.1136/oemed-2016-103953