Woman who work night shifts have a 29% higher chance of losing their baby, according to new research.
Those working a combination of days, evenings and nights are also 22% more likely to suffer menstrual disuption, making it harder to conceive.
Less impact on daily routines
Study lead Dr Linden Stricker suggested that working shift patterns with less impact on daily routines was beneficial but stressed that "the optimal shift pattern to maximise reproductive potential is yet to be established".
"There are an awful lot of different factors to take into account, like how shifts may disrupt social interaction and lead to psychological issues for example," she added.
Links between shifts and fertility
The team from the University of Southampton analysed links between shift patterns and fertility over the past 44 years.
In establishing the link between shifts and fertility problems, the team identified that shift workers have trouble sleeping and develop activity levels that are "out-of-sync with their body clocks".
Women working occasionally outside normal hours had an 80% increased rate of subfertility when they were trying to get pregnant.