Grant: Project Grant - PA: Data Analysis Using Existing Databases and Cohorts

Currently almost 20% of Canadian women enter pregnancy with a BMI in the obese range. Appropriate weight gain during pregnancy helps to improve outcomes for both mothers and their babies in women of all weights, including obese women. Due to limited and controversial findings of current studies, there is no tailoring of weight gain recommendations during pregnancy by severity of obesity. Although weight loss during pregnancy is not recommended, it has been shown that 5-8% of obese women in general, and up to 15% of women with extreme obesity, reported intentional weight loss during pregnancy. Given that a clinical trial of weight loss during pregnancy is not ethical, a high-quality observational study is greatly needed to explore potential harms of intentional weight loss during pregnancy for mothers and their babies. Our study will use Ontario birth registry data to examine the impact of weight loss during pregnancy on a wide range of adverse maternal and infant outcomes among obese women, divided into more precise obesity classes. Our study will overcome limitations of previous studies and fill research gaps by investigating dose-response effects of weight loss during pregnancy on perinatal outcomes. The study findings will inform prenatal counseling and help guide weight management during pregnancy and improve the quality of care for obese women. The current study will provide relevant, contemporary evidence of short-term perinatal outcomes of intentional gestational weight loss among obese women. Future research is needed to create optimal weight gain trajectories specific to obese women, based on their severity of obesity.