Limiting weight gain during pregnancy can not only benefit the health of the mother and child, but it can also reduce the chance of a caesarean section, according to new U.K. research.

Carried out by researchers from the International Weight Management in Pregnancy (i-WIP) Collaborative Group at Queen Mary University of London, the study is the largest research project in the world looking at lifestyle interventions in pregnancy.

The team looked at the effect of dieting (such as restriction of sugar-sweetened beverages, promoting low-fat dairy products, increase in fruits and vegetables)and physical activity (moderate intensity including aerobic classes and stationary cycling, and resistance training for muscle groups) to manage weight during pregnancy using individual participant data from 16 countries involving over 12,526 women.

They found that these interventations consistently reduced gestational weight gain, by an average of 0.7 kg compared to the control group, and still held true even after age, pregnancy history, ethnicity, BMI and existing medical conditions were taken into account.

The interventions were also associated with around a 10 per cent lower risk of caesarean section, which can carry risks such as infections for the mother and breathing difficulties for the baby.

Professor Shakila Thangaratinam from QMUL's Barts Research Centre for Women's Health said, "For every 40 mothers who follow the healthy diet and moderate exercise, one less woman will end up with a caesarean section."

However, the interventions showed no effect on the risk of stillbirth, birth weight, or admission to an intensive care unit once the child was born.

When additional data was added in from other studies the team found these interventions also reduced the risk of gestational diabetes by 24 per cent.

Professor Thangaratinam said, "Our findings are important because it is often thought that pregnant women shouldn't exercise because it may harm the baby. But we show that the babies are not affected by physical activity or dieting, and that there are additional benefits including a reduction in maternal weight gain, diabetes in pregnancy, and the risk of requiring a caesarean section."

The results can be found online published in the .