Are North American moms any different? Probably not. Some people believe that pregnancy is a free pass to eat whatever you want. The thought is that your going to get fat anyway.
Researchers from the North East Public Health Observatory studied nearly 37,000 women at a local maternity unit over 15 years.
Maternal obesity had risen from 9.9% in 1990 to 16% in 2004, they found.
If this trend continues, by 2010, 22% of pregnant women will be obese, putting a strain on maternity services, researcher Nicola Heslehurst and colleagues warn.
Being overweight during pregnancy is a big health risk for both mother and baby.
Obese mums-to-be are more likely miscarry, experience pre-eclampsia and dangerous blood clots or need a Caesarean section to deliver the baby, which is likely to be larger itself.
According to Confidential Enquiries into Maternal and Child Health, obesity is a feature of 35% of maternal deaths.
Babies of obese mothers also face a higher death risk.
Professor John Wilkinson, director of North East Public Health Observatory, said: "Maternal obesity is something that has crept up on us.
"We had anecdotal evidence and were aware that heavier women were coming in to book a pregnancy, but we needed some hard evidence."
Professor Carolyn Summerbell who heads up the Centre for Food, Physical Activity, and Obesity research at the University of Teesside said: "Future research programmes aimed at preventing the continuation of this trend are imperative."