Women's perceptions of their bodies may sway their risk of excessive weight gain during pregnancy, a new study suggests.
The study, which followed more than 1 500 women during pregnancy, found those with misperceptions about their pre-pregnancy weight were more likely to gain too many pregnancy pounds.
The odds of excessive weight gain were greatest among women who were overweight or obese before pregnancy but thought their weight was in the normal range.
However, normal-weight women who thought they were overweight were also at increased risk of excessive pregnancy pounds.
The reasons for the findings are not clear, the researchers point out in the online journal BMC Pregnancy and Childbirth.
They speculate, however, that the high prevalence of obesity in the US might be one reason that some overweight women in the study considered their weight "normal," and in turn, gained more than is recommended during pregnancy.
On the other hand, normal-weight women who thought they were heavy might have a higher rate a "disordered eating behaviours" - like bulimia or binge-eating - that could contribute to excess weight gain.
"But it isn't clear yet whether these are the explanations," lead researcher Dr. Sharon Herring, of Temple University School of Medicine in Philadelphia, said in a written statement.
"More work," she added, "needs to be done to understand perceptions of weight among mothers at the start of pregnancy, and to determine if correcting misperception reduces the likelihood of excessive pregnancy weight gain."
In general, it's recommended that normal-weight women gain 25 to 35 pounds (about 11kg to 15kg) during pregnancy, while overweight women should put on 15 to 25 pounds.
Of the 1 537 women in the current study, most were accurate when asked to describe their pre-pregnancy weight as normal, underweight or overweight. However, 13 percent of normal-weight women considered themselves overweight, while 14 percent of overweight or obese women underestimated their weight.
Compared with normal-weight women who accurately assessed their weight status, overweight women with inaccurate perceptions were nearly eight times more likely to gain too much weight during pregnancy.
The risk of excessive weight gain was two-fold higher among women who were normal-weight before pregnancy but perceived themselves as overweight.
While women need to gain a certain amount of weight for a healthy pregnancy, there are also hazards associated with excessive weight gain. Women who gain too much weight may have larger babies, resulting in a higher risk of labour complications and cesarean delivery; some studies have also linked mothers' pregnancy pounds to the risk that their children will become overweight.
Women's own long-term health may be affected as well, as excess pregnancy pounds are tougher to lose.