Objective. To investigate the association between pre-pregnancy overweight/obesity and pregnancy-related pelvic pain. Design: Nested case-control study. Setting and population. The Danish National Birth Cohort, a cohort of pregnant women and their children recruited 1996–2002. Methods. The women were interviewed twice during pregnancy and twice after childbirth. The first pregnancy interview provided information on self-reported pre-pregnancy body mass index (BMI) and possible confounders, while data on pregnancy-related pelvic pain came from an interview sixmonths postpartum. Cases (n=2 271) were selected on the basis of self-reported pelvic pain, and controls were randomly selected among women who did not report pelvic pain (n=2 649).We used logistic regression analysis to calculate pregnancyrelated
pelvic pain odds ratios (OR (95% confidence intervals)) according to prepregnant
BMI.Main outcomemeasure. Self-reported pregnancy-related pelvic pain.
Results. In the total cohort, 18.5% of all pregnant women reported pregnancyrelated pelvic pain. In the nested case-control study, the adjusted ORs for overall pelvic pain were 0.9 (0.7–1.2) in underweight women, 1.2 (1.1–1.4) in overweight women, 1.5 (1.2–2.0) in obese women Class 1 (30=BMI<35), and 1.9 (1.3–2.8) in obese women Class 2 + 3 (BMI=35), all relative to normal weight women. The correspondent ORs for severe pelvic pain were 0.8 (0.6–1.2), 1.4 (1.2–1.7), 1.7 (1.3–2.2), and 2.3 (1.6–3.4). The associations were stronger among women who had not given birth before. Conclusion. The risk of pregnancy-related pelvic pain increasedwith pre-pregnancy BMI in an exposure–response relation and potentially adds another maternal complication to obesity.