Causes of SPD
Recent research in the U.K. indicates that approximately one in 36 pregnant women suffer from some level of SPD (see Ref.). Some ethnic groups report a higher incidence, especially Scandinavian women, but this may be due to better reporting of the condition and their tendency towards more ‘hightech’ births.
Theories about the possible causes of SPD include:
- Misalignment of the pelvic bones: the bones don't line up correctly in front (at the symphysis pubis) resulting in additional pressure on the symphysis pubis cartilage. This misalignment tends also to affect the back, especially in the sacro-iliac area, due to the interconnected nature of the pelvic bones.
- Evidence suggests that pelvic misalignment following birth is often associated with babies who present with the occiput posterior. This is when the occipital bone (back of the skull) of the baby is posterior. The baby is head down but facing towards the symphysis pubis. This can increase symphysis pubic bone discomfort and backache in late pregnancy.
- Different theories suggest that the pregnancy hormones relaxin and progesterone may occur at higher levels in some women, causing excessive relaxation of the pelvic ligaments Another theory is that some women manufacture excessive levels of relaxin during pregnancy, causing pelvic laxity. However, although still popular, this theory seems to have been disproven by recent research.
- Some women may experience hyper-mobility in all their joints due to genetic factors. The relaxing hormones of pregnancy may worsen this condition, leading to pelvic instability.
- Previous trauma or accidents involving damage to the pelvic area may increase the risk of developing SPD.
- Some interventions and positions used during labour and birth are considered to place stress on the symphysis pubis joint.
- Diastasis Symphysis Pubis (DSP). This condition occurs when there is a widening of the gap between the pelvic bones at the symphysis pubis. In pregnancy, the gap widens by 2.3 mm to allow for birth, but post-partum the supporting ligaments tighten to reduce the gap to 1 cm or less. Where excessive strain, mishandling or damage has occurred, the pubic symphysis can become abnormally separated causing severe pain postpartum. An abnormal postpartum gap is defined as 1 cm or more after the time when the joint should be back to normal (DSP). The natural extra widening returns to normal after a few days but the supporting ligaments will take 3-5 months to return to their fully functioning state.
Reference: Owens K, Pearson A, Mason G. ‘Symphysis Pubis Dysfunction - a cause of significant obstetric morbidity’. European Journal of Obstetric, Gynaecological and Reproductive Biology 2002 Nov 15; 105(2): 143-6.