Pregnant women who work nights or long hours may be more likely to have a miscarriage or preterm delivery than mothers with day jobs, a Canadian review suggests.

With night shifts, pregnant women were 21% more likely to have preterm deliveries and 23% more likely to have miscarriages than women who worked days, the analysis found.

Working more than 40 hours a week was also associated with a 38% higher risk of miscarriages and a 21% higher risk of preterm deliveries than working less.

In other key findings from the review of 62 studies, which included almost 197,000 women: