Smoking during pregnancy or being overweight beforehand could account for two fifths of the social divide in childhood obesity, according to a new study.
Researchers called for policies to help mothers keep a healthy weight, abstain from smoking and breastfeed their infants to help combat childhood obesity.
Weight problems are more common in children from disadvantaged backgrounds, although it has not been clear how their early life affects their weight.
Researchers looked at the height and weight of 11,764 children from the Millennium Cohort Study of children born between September 2000 and January 2002 for their study.
They also looked at detailed questionnaires completed by their mothers which included their weight before and during pregnancy and whether they smoked during their pregnancy.
They also considered whether children were born by caesarian section, whether they were breastfed and the age when they were weaned onto solid food.
The research, by a team from the Department of Public Health at Liverpool University and the Institute of Child Health at University College London, published in the Archives of Disease in Childhood also considered the mothers’ educational qualifications.
A fifth of children whose mothers had fewer educational qualifications were overweight compared with a quarter of those with mothers educated to degree level or above.
They found that women’s weight before pregnancy and their smoking habits during pregnancy accounted for two fifths of the difference in children’s risk of being overweight.
The researchers said “a considerable amount of the social inequalities in pre-adolescent overweight” can be explained by their mother’s weight and smoking before and during pregnancy.
The more mothers smoked during pregnancy, the greater the risk their children would be obese, the study found.
It said the impact of smoking can influence the family budget and choice of cheap, poor quality foods.
Shorter periods of breastfeeding may make a small contribution to childhood obesity too, said the authors.