Influence of some biomechanical factors on low-back pain in pregnancy.

Several biomechanical factors were recorded intermittently in 855 pregnant women from the 12th to the 36th week of gestation and were related to back pain occurrence during pregnancy. The three factors related to the development of back pain were abdominal sagittal diameter, which correlated with back pain, with a coefficient of 0.15 (P < 0.01); transverse diameter (r = 0.13, P < 0.01); and depth of the lumbar lordosis, which correlated with a coefficient of 0.11 (P < 0.01). In the group of women who were pregnant for their first time, there was a significantly lower peripheral joint laxity in the 12th week in those women who, later in pregnancy, developed back pain. These correlations suggest that back pain in pregnancy can not be explained primarily by biomechanical factors.