2639 women met inclusion criteria, with BMI 30 kg/m2 present in 39% of
participants. Obese women had higher rates of pregnancy redating
compared to non-obese women—adjusted risk ratio [aRR] 1.23 (95%
confidence interval [CI] 1.07-1.41). Class III obese women were more
likely than any other BMI class to have their pregnancies redated by
ultrasound–aRR 1.46 (95% CI 1.18-1.80). Analyses adjusted for age, race,
and parity showed that for each unit increase in BMI over 30 kg/m2,
women had a 2 percent increased risk of being redated (p<0.001). Mean
EDD by ultrasound minus mean EDD by LMP was -0.98, -2.70, -2.43, and
-3.35 (p<0.001) for non-, class I, class II, and class III obese
women, respectively.