Women who work more than 40 hours a week or routinely lift heavy loads may take longer to get pregnant than women who don’t, a US
Researchers followed 1,739 nurses who were trying to get pregnant and
estimated 16 per cent of them failed to achieve this goal within 12
months, and five per cent still hadn’t conceived after two years.
Working more than 40 hours a week was linked with taking 20 per cent
longer to get pregnant compared to women who worked 21 to 40 hours.
Moving or lifting at least 11-kilogram loads several times a day was
also tied to delayed pregnancy, extending the time to conception by
about 50 per cent.
“Our results show that heavy work, both in terms of physical strain
and long hours, appears to have a detrimental impact on female nurses’
ability to get pregnant,” lead study author Audrey Gaskins, a researcher
at Harvard T.H. Chan School of Public Health in Boston, said by e-mail.
Most healthy couples can conceive within three to six months, though
the process can take longer for people who are older or who have
fertility compromised by certain medical conditions or by smoking or
For the current study, Gaskins and colleagues reviewed data on women
participating in a nationwide survey of nurses between 2010 and 2014 who
at some point said they were trying to conceive.
Half of the women were at least 33 years old, about 44 per cent were
overweight or obese and 22 per cent were current or former smokers.
The majority of the women worked exclusively days or nights, though
16 pe rcent of them had rotating shifts at different times. About
one-third of the women were on their feet for at least eight hours a
day, and 40 per cent reported lifting heavy loads up to five times a
Frequency of night shifts or the duration of rotating or non-rotating
evening work wasn’t linked to the time it took women to conceive, the
When researchers excluded women who had irregular menstrual cycles,
which can independently impair fertility, they still found that heavy
lifting was linked to a 33 per cent longer timeline to conception. The
impact of heavy lifting was also more pronounced for overweight and
It’s possible that certain working conditions might make pregnancy
more likely, and it’s also possible that women who struggle to get
pregnant may choose to work longer hours, the researchers acknowledge in
Occupational and Environmental Medicine.
There also may be a much simpler explanation for the delayed times to
conception for women who work more or come home more physically
exhausted from lifting multiple heavy loads, said Courtney Lynch, a
specialist in reproductive health at Ohio State University in Columbus.
“If this effect is real, it is likely due to the fact that these
women are having less frequent intercourse due to their work demands,”
Lynch, who wasn’t involved in the study, said by e-mail.
Couples who want to get pregnant faster should have sex at least
twice a week, and not only on weekends, she advised. Women should also
maintain a healthy weight, get enough exercise and avoid smoking and
When women struggle to conceive, they may consider using devices that
help track ovulation, Lynch added. Often sold as fertility monitors,
some of these devices pinpoint ovulation by testing urine for spikes in
certain hormones during that time of the month.
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