Impact of updated Institute of Medicine guidelines on prepregnancy body mass index categorization, gestational weight gain recommendations, and needed counseling

Abstract

Background: Our objective was to quantify how the 2009 revisions of the 1990 Institute of Medicine (IOM) gestational weight gain (GWG) guidelines change women's body mass index (BMI) categorization and BMI-specific GWG adherence categories. The goal was to identify how provider counseling practices need to change on a population level. Methods: A retrospective review of automated labor and delivery records from a tertiary care hospital in Central Massachusetts was performed. The study cohort included women who delivered singleton, live birth gestations from from April 1, 2006, to September 30, 2009. Records missing weight, height, GWG, gestational age (GA), and/or GA <22 or>43 weeks were excluded. BMI groups and GWG adherence were categorized according to IOM 1990 and 2009 recommendations. Adherence analyses included full-term gestations only. Results: The cohort consisted of 11,688 women, mean age 28.9 (+/-6.1) years and mean parity 1.0 (+/-1.1). By 1990 recommendations, 10.1%, 52.5%, 14.1%, and 23.3% gravidas were low weight, normal weight, high weight, and obese; and 19.8%, 33.3%, and 46.9% were undergainers, appropriate gainers, and overgainers, respectively. By 2009 recommendations, 3.9%, 51.3%, 24.5%, and 20.3% gravidas were underweight, normal weight, overweight, and obese, and 16.7%, 30.8%, and 52.6% were undergainers, appropriate gainers, and overgainers, respectively. Differences in categorization by guideline year was significant for BMI category (p<0.0001) and GWG adherence (p<0.0001). Compared to 1990 guidelines, 16.7% of women were classified differently using 2009 guidelines, with fewer classified as underweight, normal weight, or obese and more as overweight; 17.1% of 1990 appropriate gainers would be classified as overgainers, given new guidelines. Conclusions: Changes in IOM GWG recommendations alter gravidas' BMI categories and, thus, the recommended GWG. As the amount advised is associated with actual gain, accuracy is paramount. GWG is a modifiable parameter associated with immediate and long-term maternal/neonatal health outcomes, and counseling can have a significant public health impact and should involve BMI determination, followed by BMI-specific GWG recommendations in accordance with current guidelines.