Pregnancy-related pelvic pain is more frequent in women with increased body mass index

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 six months 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 pregnancy-related pelvic pain odds ratios (OR (95% confidence intervals)) according to pre-pregnant BMI. Main outcome measure. Self-reported pregnancy-related pelvic pain. Results. In the total cohort, 18.5% of all pregnant women reported pregnancy-related 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 increased with pre-pregnancy BMI in an exposure-response relation and potentially adds another maternal complication to obesity.