Women's reported weight: Is there a discrepancy?

Objective: To compare self-reported pre-pregnancy weight & delivery weight with documented pre-pregnancy & delivery weight and determine whether there are differences compared with the Institute of Medicine's (IOM) guidelines. Methods: This is a retrospective analysis of 234 women. Inclusion criteria included documented height, self-reported pre-pregnancy weight, self-reported delivery weight, documented pre-pregnancy weight ± 12 weeks from last menstrual period, and documented delivery weight ± 2 weeks from delivery. We determined the difference between self-reported pre-pregnancy weight vs. documented pre-pregnancy weight and self-reported delivery weight vs. documented delivery weight. Using documented pre-pregnancy weight and documented delivery weight, we calculated gestational weight gain (GWG) relative to IOM criteria. Results: Self-reported pre-pregnancy weight was 2.94 kg less than documented pre-pregnancy weight (p < 0.0001). Self-reported BMI was 1.11 mg/kg² less than documented BMI (p < 0.0001). Self-reported GWG was 3.01 kg greater than documented GWG (p < 0.0001). Ninety-eight percent of normal weight correctly classified pregravid BMI in contrast to 86% of obese (p < 0.005) and 73% of overweight (p < 0.001). Conclusions: Overweight and obese women underestimated self-reported pre-pregnancy weight & overestimated GWG, thereby mistakenly categorizing IOM guidelines.