Increasing prepregnancy body mass index: analysis of trends and contributing variables

In the United States, obesity has increased steadily. As obesity in pregnancy is a high-risk obstetric situation, important questions are whether there has been a trend toward higher prepregnancy body mass indexes (BMIs) in women who have become pregnant and if there are subgroups at risk. The objective of this study was to analyze the shifts, if any, in the prepregnancy BMIs in women who delivered.

Analysis of the birth certificate data collected in a regional perinatal data system of all live born deliveries (79,022 cases) occurring in a contiguous 8-county area in upstate New York from 1999 to 2003.

From 1999 to 2003, there was an overall increase in the mean prepregnancy BMI of the total delivery population (P < .01). There was a relative 11% increase in the Institute of Medicine (IOM) overweight (P < .01) and a relative 8% increase in the obese (P < .01) categories. There was an increase in the numbers of women in the IOM overweight or obese categories in these subgroups (P < .05): age (all subgroups), ethnicity (white and black), education (all subgroups), insurance type (all subgroups), previous live births (all subgroups), urbanization status (all subgroups), median family income of ZIP code area (all subgroups), and smoking (both smokers and nonsmokers).

There was a significant increase toward higher prepregnancy BMIs across multiple subgroups. Our study demonstrates that increased prepregnancy BMI is an issue that spans almost the entire spectrum of subgroups of patients who delivered.