Gestational diabetes could affect a lot more women than estimated earlier, as much as 16 per cent of the pregnant, new study shows.
Researchers warned that doctors should be vigilant to monitor for the condition, which is linked to an increased risk of going into labour prematurely and other complications.
Previously doctors had thought that between five and eight per cent of women suffered from the condition during their pregnancy.
But a new international study involving 23,000 women in nine countries suggests that more than twice as many mothers to be, 16 per cent, developed the disease.
Diabetes in pregnancy can also increase the risk of suffering from pre-eclampsia, a potentially fatal condition where the mothers blood pressure rises to dangerously high levels, and of a caesarean section delivery.
Also known as gestational diabetes, the condition is triggered by changes in certain hormones which affect how insulin is used by the body.
The disease usually develops in the second half of pregnancy and disappears again after labour.
"As result of this study, more than 16 per cent of the entire population of pregnant women qualified as having gestational diabetes," said Dr Boyd Metzger, from Northwestern University in Chicago, who led the study.
"Before, between 5 to 8 per cent of pregnant women were diagnosed with this."
Dr Metzger added: "We shouldn't be surprised.
"The fact that we have a lot of gestational diabetes to deal with is consistent with the major impact that diabetes and obesity are having in our population at large.
"How could we expect pregnancy to escape that?"
The study also found that blood sugar levels traditionally used to diagnose patients with the condition were set too high.
The findings will be published in the journal Diabetes Care.