Class III obesity and unwanted pregnancy among women with live births in New York City, 2004-2007.

Obesity is associated with numerous adverse health effects for pregnant women and their newborns. Unintended pregnancy is associated with suboptimal prenatal health behaviors and adverse birth outcomes. While research has suggested a link between obesity and unintended pregnancy, the evidence has been contradictory. Research has not focused on women at the highest level of obesity, Class III (body mass index ≥40). Pregnancy Risk Assessment Monitoring System data for 4,161 women in New York City with a live birth from 2004 to 2007 and complete data on pregnancy intention, height, and weight were examined. The primary outcome, having a live birth that resulted from an unwanted pregnancy (not wanted at that time or at any time in the future), was compared across 6 groups of pre-pregnancy body mass index (BMI). Logistic regression models adjusting for sociodemographic factors and stressors during pregnancy were conducted. The proportion of women reporting their pregnancy was unwanted increased with increasing BMI level to a high of 24 % among women with Class III obesity. After adjustment for confounding sociodemographic factors, women classified as Class III obese were significantly more likely than women with normal BMI to report an unwanted pregnancy [AOR = 2.81 (95 % CI: 1.41-5.60)]; this relationship held after adjusting for stressors during pregnancy. No significant association was found for women of other BMI groups. Previous analyses may have masked a relationship between BMI and unwanted pregnancy among women with Class III obesity. Further research exploring underlying mechanisms which are amenable to intervention is of critical public health importance.