The two halves of your pelvis are connected at the front by a stiff joint called the symphysis pubis. This joint is strengthened by a dense network of ligaments which means that under normal conditions, very little movement occurs. In order to make your baby's passage through your pelvis as easy as possible, your body produces a hormone called relaxin, which softens the ligaments in your pelvis. As a result, these joints move more during and just after pregnancy.
We are not sure exactly what causes SPD but current thinking indicates that if one side of the pelvis moves more than the other when you walk or move your legs, this can lead to pain and inflammation at the symphysis pubis. X-rays and scans may not diagnose the problem as this rotation does not show up on most scans. Many women with SPD experience significant pain without any great separation of the joint -- the amount of pain isn't related to the degree of separation.
A related condition is diastasis symphysis pubis (DSP) in
which the pubic joint loosens and leaves an abnormally wide gap between the two pelvic bones. The average gap between the bones in a non-pregnant woman is 4-5mm and during pregnancy it's normal for this gap to widen by 2-3mm. If the gap is 10mm or more, DSP is diagnosed. This is a rare condition and can only be diagnosed by X-Ray.
Pain in the pubic area and groin are the most common symptoms. You may also suffer from back pain in pregnancy, Pelvic Girdle Pain (PGP) or hip pain. It is common to feel a grinding or clicking in your pubic area and the pain may travel down the inside of the thighs or between your legs. The pain is usually made worse by separating your legs, walking, going up or down stairs or moving around in bed. It is often much worse at night and can stop you getting much sleep. Getting up to go to the toilet in the middle of the night can be especially painful.
wasn't before though 
