Lower back pain in pregnancy is very common. It is estimated that as many as 50% women will develop some kind of back problem during pregnancy. The symptoms comes from a variety of structures including sacroiliac joints, lower back structures and sometimes the sciatic nerve .There are a few different reasons why this might happen..
The pelvis is made up of two large bones, the ilium, and they attach to the sacrum at the back of the spine. Where the ilium and the sacrum meet, is the sacroiliac joint.
The sacroiliac joint is a pretty special joint, normally it barely moves at all. It’s a very stable joint. This is partly due to the shape of it – both the surfaces of the ileum and the sacrum are knobbly and fit to together very snugly. Further support for the joint comes from very large strong ligaments and from some of the key muscle groups that surround it
In order to give birth and let a relatively large object (baby) through the narrow pelvic canal the pelvic bones have to be able to move and widen.In order for the baby to be born the sacroiliac joint needs to move so that the two halves of the pelvis can adjust and allow delivery.
To enable this the body releases a hormone called relaxin which causes the bodies ligaments to soften and relax. This affects the whole body including the lower back but it especially affects the sacroiliac joints. The sacroiliac joints are supported by large, tough ligaments and these ligaments must soften to allow delivery.
This is what you need when you are giving birth but the effects are not so good both before and after birth as the large, strong ligaments supporting your back and sacroiliac joints are not so supportive.
As your pregnancy progresses this relaxing of the ligaments increases. Combined with changes in your centre of gravity and increased weight because of the baby the likelihood of back pain increases.
It’s also worth thinking about the effect of the hormone relaxin on the other ligaments in the back. It is not selective, all ligaments become lax, even your knee joints when you are pregnant. So it’s not really surprising that back problems during early pregnancy occur.
To make matters worse if you had poor muscle tone, so less supportive core stability muscles, or a history of back pain before getting pregnant its more likely that you will get back pain in pregnancy.
This means that your posture has to rapidly adapt to compensate for this. This happens by increasing the hollow or the lordosis in the small of your back
Changes02-Mar-2015more vulnerable and so repetitive lifting or bending during pregnancy may worsen your lower back pain problem.
The other important thing to consider is that women who are pregnant can get all the regular types of back pain too and that it may not be related to pregnancy at all.
I have written a page that has lots of helpful suggestions for you here
1. Whitcome, K. K., Shapiro, L. J. & Lieberman, D. E. Nature advance online publication, doi:10.1038/nature06342 (2007)
Kalus, S.M., Kornman, L.H. & Quinlivan, J.A. Managing back pain in pregnancy using a support garment: a randomised trial. BJOG 115, 68-75 (2008).
Ho, S.S.M. et al. Effectiveness of maternity support belts in reducing low back pain during pregnancy: a review. J Clin Nurs 18, 1523-1532 (2009).