2.2. Variables Pre-pregnancy body-mass index (BMI) was calculat- ed using the subject's height and pre-pregnancy weight [1]. Pregnancy weight change was the difference between pre-pregnancy weight and the last weight measured prior to delivery, if the last measurement was within one week of delivery. To estimate pregnancy weight gain for the 270 sub- jects last weighed one to four weeks before delivery, their average weekly weight gain times the number of weeks between measurement and delivery was added to their last measured weight. In a sensitivity analysis, total pregnancy weight gain was estimated for these 270 subjects by adding 0.74 lbs per week, the average weight gain between 30 and 40 weeks of pregnancy [1].