Mechanically the symphysis pubis serves to anchor the ends of the two weight bearing arches of the pubis-the femorosacral and ischiosacral arches. Under normal conditions it has been found to exceedingly resistant to separation. Sacroiliac strain is also uncommon because the sacroiliac ligaments are very strong and the movement which produce a torsion strain upon the joint is more likely to cause a strain of thinner capsular ligaments surrounding the small lumbosacral joints. We experienced a case of separation of the symphysis pubis and 2 cases of sacroiliac strain during and after spontaneous labor.