Overweight or obese mums who underestimate their weight status are more likely to over-gain during pregnancy

Women who misperceive their body weight are more likely to gain too much weight during pregnancy. A study published today in the open access journal BMC Pregnancy and Childbirth has shown that a poor estimation of one’s own size at the beginning of pregnancy is associated with excessive gestational weight gain, in both normal weight and overweight or obese women.

The research was carried out by a team of researchers led by Sharon Herring, MD, MPH, an Assistant Professor of Medicine and Public Health at Temple University. She said, “Compared to normal weight women who accurately assessed their pre-pregnancy weight status, the odds of gaining excessively during pregnancy were increased seven-fold among overweight and obese women who thought they weighed less than they really did. Normal weight women who thought they were overweight had twice the odds of excessive gestational weight gain.”

The authors studied 1537 women enrolled in Project Viva, a US birth cohort, who were normal weight, overweight or obese at the beginning of their pregnancies. Underweight women were not included. Of the 1029 normal weight participants, 898 (87%) correctly reported that they were normal weight just prior to pregnancy, while 131 (13%) incorrectly thought they were overweight or obese. Of the remaining women who were overweight or obese, 438 (86%) accurately perceived their body weight status, while 70 (14%) under-assessed their size before pregnancy. Compared with normal weight women who accurately perceived their pre-pregnancy weight status, overweight or obese under-assessors were younger, more likely to be non-white, of lower income, less educated, and single. These women consumed fewer fruits and vegetables during their pregnancies, but did not differ from normal weight accurate assessors in amount of vigorous activity or fried food intake. Normal weight over-assessors, on the other hand, were relatively similar in all characteristics to their accurate assessor counterparts.

Although the reasons for misperceived body weight aren’t completely understood, the authors speculate that the high prevalence of the obesity in the US may affect women’s judgement about their respective weight status. By failing to recognize their overweight or obese status, these women may be less likely to follow pregnancy weight gain guidelines. Herring said, “As excessive gestational weight gain increases the risk of poor maternal and child outcomes, including higher rates of caesarean sections, larger babies, and greater difficulty losing weight after delivery, more work needs to be done to determine if correcting this misperception reduces the likelihood of excessive pregnancy weight gain.”