['The aim of this study was to investigate the association between pregnancy-related pelvic pain (PRPP) and sacroiliac joint (SIJ) laxity.', 'A cross-sectional analysis was performed in a group of 163 women, 73 with moderate or severe (PRPP+) and 90 with no or mild (PRPP-) PRPP at 36 weeks of pregnancy. SIJ laxity was measured by means of Doppler imaging of vibrations in threshold units (TU). Pain, clinical signs and disability were assessed with visual analog scale (VAS), posterior pelvic pain provocation (PPPP) test, active straight leg raise (ASLR) test, and Quebec back pain disability scale (QBPDS), respectively.', 'Mean SIJ laxity in the PRPP+ group was not significantly different from the PRPP- group (3.0 versus 3.4 TU). The mean left-right difference, however, was significantly higher in the PRPP+ group (2.2 TU) than in the PRPP- group (0.9 TU). In the PRPP- group, only 4% had asymmetric laxity of the SIJs in contrast to 37% of the PRPP+ group. Between the PRPP+ subjects with asymmetric and symmetric laxity of the SIJs significant differences were found with respect to mean VAS for pain (7.9 versus 7.0), positive PPPP test (59% versus 35%), positive ASLR test (85 versus 41%) and mean QBPDS score (61 versus 50).'] Is pelvic pain during pregnancy associated with asymmetric laxity of the sacroiliac joints?