The increased load of the baby in the belly causes the pelvis to anteriorly tilt and throws the hips and knees into the locked position. This also puts the lumbar spine into an extension or locking position. Hence the weight of the mother’s body and the weight of the baby are now ‘hanging on the joints’ of the lumbar spine.At the same time the mother’s ligaments are softening due to the circulating hormone relaxin. This may result in the joints being stretched well beyond their normal range of motion.
Hence pregnancy puts extra load on the lumbar spine and may exacerbate existing low back pain or cause new onset of low back pain.
Why does it happen to me and not everyone?
This may be due to genetic factors, the shape of your spine/pelvis, and/or the ‘normal’ laxity in your joints. Hyper-mobile individuals are probably more likely to have back pain with pregnancy. It may also be due to the external load that you apply to your body – women who are standing for a long time put more load on their spine. A larger baby will also stress the spine more.
Will this last the whole pregnancy and will it get better following pregnancy?
This can be variable and depends on how irritated the spine is and also the demand that the mother is placing on her body during pregnancy. During pregnancy it is important to work hard on posture to train your muscles to take the load off the joints.
During pregnancy you need to rest frequently and not place prolonged strain on the joints (especially standing). Following pregnancy, whilst the load has gone from the belly, the joints are still lax as the pregnancy hormones remain active on the ligaments for around 6 months following the cessation of breast-feeding.
Stance habits obtained during pregnancy are very hard to break. Hence, the pain may not immediately go away unless the mother works on the reasons why it started in the first place.
Some tips to help your back pain
Keep good posture
Avoid prolonged standing especially on hard surfaces and high healed shoes
Try to lie with a pillow under your top leg and sleep on your side
Bend the knees to lift or pick up objects
Assess and change your ergonomics (work and home life) – especially change tables, cots and toddlers
Don’t rush or push yourself. Take plenty of extra rest during your pregnancy
If you cough or sneeze try to brace you abdominals
Try not to strain i.e. on the toilet or moving heavy objects
Light exercise will help your back – pool exercise can be beneficial.
The pain sometimes goes down my leg – how does that come from the back?
Problems with the joints of the back can be perceived by your brain as coming from an area that is geographically separate to the spine. This mechanism is known as ‘convergence” and is the same sort of reason that amputees get ‘phantom limb pain’.
Once I have had a back problem will it always be a problem?
Not necessarily. Postpartum the pain may go completely, however, once you have had a first attack of low back pain, your body changes the way it supports the spine. Subsequent back pain can then happen more easily. This is due to the fact that your body has lost its protective mechanisms for the spine (the core muscles and the pelvic floor muscles). You may find if you have another baby that the pain is worse with the next pregnancy unless you address the weakness in the core muscles (pelvic floor, transversus abdominis). Physiotherapists can train you to rehabilitate your muscular system to protect your spine.
Do I need to get a scan to assess my back pain?
X-rays are unable to be used during pregnancy. Further imaging is probably not required but your doctor and/or specialist would decide this on a case by case basis.
Can I use medication? Will it harm the baby?
Pregnant women should never take any medication without first consulting their doctor.
What else can I use for the pain?
You could try using TENS (nerve stimulating machines used for labour pains) after the first trimester. You may find that gentle soft tissue techniques such as massage and mobilisation of the lumbar joints can ease the symptoms. Sometimes a pelvic brace (support) can help.
Should I do sit-ups to strengthen my back again?
No. Sit-ups can make the problem worse. During sit-up activity the hip flexors are maximally loaded and they can then stress the mid lumbar facet joints. Abdominal muscles support the back but sit-ups are not the way to work them. It is best to get a physical therapist to guide you through exercises appropriate to your problem.