Night shift impact on pregnant women inconclusive

Some studies have suggested that working the night shift may raise a pregnant woman's risks of preterm delivery or having an underweight baby, but a review says that if those effects exist, they are likely to be small.

After looking at 23 studies involving thousands of women, researchers led by Matteo Bonzini of the University of Insubria in Italy found that overall, shift work was not strongly linked to the risk of preterm delivery versus a standard nine-to-five job.

Women working night or rotating shifts did have a slightly higher chance of having a baby who was small for gestational age, but the evidence was not strong enough to make "confident conclusions", the researchers report in the journal BJOG.

"On balance, the evidence currently available about the investigated birth outcomes does not make a compelling case for mandatory restrictions on shift-working in pregnancy," they write.

As for birth size, there were somewhat higher risks seen among women doing shift work - they were 12 percent more likely, for example, to have a baby who was small for gestational age.

But the evidence was not statistically strong, and the increased risk could be a chance finding, the researchers say.

They add that there is a need for further studies.

"In the meantime, we suggest that it would be prudent, insofar as job circumstances allow, to permit pregnant women who wish to do so to reduce their exposure to shift and night working," they write.