Objective: Misclassification of body mass index (BMI) by pregnant women could be a significant barrier to minimizing weight-related adverse pregnancy outcomes and improving the short- and long-term health of mother and child. The primary objective in this study was to determine the proportion of a group of pregnant women who were able to correctly classify BMI. Secondary objectives included assessing the direction of BMI misclassification and maternal knowledge of target gestational weight gain and obesity-associated pregnancy complications.
Methods: We designed a cross-sectional survey to assess misclassification of BMI and knowledge of obesity and pregnancy outcomes, and to provide information regarding the participants' sources of knowledge, their perception of appropriate weight gain in pregnancy, and basic demographic information. The questionnaire was completed by participants awaiting routine ultrasound assessment at between 11 and 24 weeks' gestation.
Results: Of 117 respondents, 30 (25.6%) were overweight (BMI 25 to 29.9) or obese (BMI ≥ 30.0). Obese or overweight women were significantly more likely to misclassify their BMI. Furthermore, they were significantly more likely to overestimate the minimum and maximum target gestational weight gains for their respective BMI classes. There were no differences between women in the various BMI categories with regard to their awareness of several common obesity-related pregnancy complications.
Conclusion: Misclassification of pre-pregnancy BMI is common, particularly among women carrying excess weight. Evaluation of pre-pregnancy BMI and education regarding appropriate gestational weight gain are logical initial steps for optimizing weight-related pregnancy outcomes.