Pelvic Dysfunction (or Separation) in Pregnancy

Generally, in normal cases of pregnancy, hormones make the cartilage soften a bit to make room for the baby and assist everything to open up easily during labor. However, in some women hormones make the cartilage too soft, and as a result the pelvis starts to separate and this can create immense pain and risk of premature delivery. The levels of pregnancy hormone peak in the 12th week of pregnancy - therefore it is common for the symptoms of pelvic dysfunction to occur around then.

From Wikipedia:
Diastasis symphysis pubis
The non-pregnant gap is 4-5mm but in pregnancy there will be an increase of at least 2-3mm due the ligaments which surround and insert into the joint as they remodel under the influence of hormones. Therefore, it is considered that a total width of up to 9mm between the two bones is normal for a pregnant woman. This natural extra gapping decreases within days following the delivery, although the supporting ligaments will take three to five months to fully return to their normal state. An abnormal gap is considered to be 1cm or more, sometimes with the two bones being slightly out of alignment. If there is a complete separation, that is, a traumatic tear, and the joint will be completely unstable. This tear can be felt and sometimes heard by the woman. There will be intensive pain followed by swelling and inflammation. The woman is unable to move her back, trunk, hips and legs without causing severe pain. When lying on her back her legs involuntary move apart and without the ability to close them together. This type of pelvic fracture needs to be treated as such and investigations into possible involvement of the sacroiliac joints should be addressed. It is important to note that the same can happen to the sacroiliac joints, and could lead to laxity and even inflammation. This involvement could involve one or both sacroiliac joint(s). A separation or diastasis can also be the result of traumatic forces from either an incident during the pregnancy or delivery.