Low back pain (LBP) and pelvic girdle pain (PGP) are common in pregnancy. The prevalence of LBP in pregnancy is around 45%, although the true incidence is almost certainly higher with some form of mechanical pain being almost universal.
Distinction must be drawn between pain that is almost a "normal" physiological experience in pregnancy and pathological pain.
‘Physiological’ pain in pregnancy
Non-specific low back pain (NSLBP), which is defined as pain below the costal margin and above the inferior gluteal folds, is the commonest form of LBP in the general and also the pregnant population. The prevalence is thought to be higher in the pregnant population due to a variety of theoretical causes; hormonal; biomechanical and even vascular.1
Risk factors may include previous history of LBP, smoking, obesity, age, depression and anxiety, exercise habits, maternal habitus. Obstetric considerations may not be relevant to LBP. Interestingly previous lumbar surgery has been identified as protective. This is counterintuitive and the exact mechanism of this effect is unclear. Younger mothers report more LBP. The stage of gestation does not affect reporting of LBP. Length of time spent in bed, but not mattress characteristics, has been shown to be important.1
PGP is defined as pain in the symphysis and/or between the posterior iliac crest and the gluteal fold, which may refer to the posterolateral thigh. This is a symptom complex that is more closely linked to the progress of the pregnancy, presentation, foetal size and previous obstetric history, including increasing parity.4 Mechanisms including increasing mechanical load, relative pelvic ligamentous instability and muscular dysfunction have been proposed.2
Differentiating NSLBP and PGP
It is useful to differentiate the two conditions as treatment differs.
The differentiation of NSLBP and PGP is based on description of the pain, especially its distribution and stage of pregnancy and examination findings. LBP is characterised by restriction of flexion, para-spinal tenderness and pain on lumbar flexion. PGP will produce pain on the posterior pelvic provocation test. The hip and knee are flexed to 90 degrees, pelvis stabilised at the contralateral iliac crest and posterior directed force along the femur produces ipsilateral gluteal pain.3
Evidence supports the use of a non-elastic pelvic support belt placed at the level of the greater trochanters in PGP but not in LBP. There is variable evidence to support pelvic and gluteal strengthening exercises in PGP. Weight-bearing exercise may be painful. Cycling is often not possible, especially in an upright position.
LBP is best managed by an active functional core and gluteal strengthening exercise programme designed specifically for the pregnant woman. General weight-bearing non-impact exercise such as walking, cycling and the use of an elliptical cross trainer will be beneficial. Swimming is also encouraged.
Pathological spinal pain
Pregnant women are susceptible to the same pathologies as the general population. As with all patients presenting with back pain consideration to ‘red flag’ symptoms should be given. Clearly the extremes of age and trauma are not relevant but past medical history, systemic symptoms, deformity and the distribution and character of pain are important.
Disc pathology is the commonest pathological condition presenting in pregnancy. Pain referring below the knee is unlikely to be PGP and raises the possibility of neural compromise. Disc prolapse is commonest in the over 30 years age group, which is becoming increasingly a larger proportion of the pregnant population.
Diagnosis is made on the description of the pain, its distribution and neurological symptoms. Physical findings such as limited straight leg raise, sciatic and femoral stretch tests may be misleading in the pregnant. Objective evidence of motor or sensory disturbance is key.
Symptoms of cauda equina compromise must be specifically sought and examination including perianal sensory disturbance and anal tone documented. Changes in sphincter function may be attributed to pregnancy and if not considered properly may lead to serious delay in diagnosis and essential intervention. One in 10,000 pregnant women will suffer disc prolapse and /or cauda equina syndrome (CES). Often the only symptom on presentation is back pain. It is not uncommon for there to be no leg symptoms and no abnormal leg neurological findings on examination.
In the majority of cases initial rest (48 hours maximum) followed by gentle mobilization with appropriate analgesia and physical therapy will suffice. Pain usually settles within four to six weeks.
If pain is unmanageable with safe analgesia or there is objective evidence of progressive neurological loss, especially CES (which necessitates immediate intervention), investigation is indicated. MRI is the modality of choice. Current advice is to avoid MRI in the first trimester due to theoretical harmful effects on the foetus, although no harmful effects have been demonstrated. However, if benefit outweighs risk after discussion with a radiologist MRI can be undertaken at any stage of pregnancy with adjustments to the protocols used.4
Treatment of refractory sciatica in pregnancy follows the same algorithm as in the general population with a conservative approach being foremost. In the presence of deteriorating neurology or CES, surgical discectomy is the preferred course of action. Non-obstetric surgery in pregnancy is associated with premature delivery and low birth weight but not congenital defects.5 LBP and PGP do not alter indications for mode of delivery.
Known symptomatic disc prolapse or recent spinal disc surgery would be a relative indication for consideration of elective Caesarean section in conjunction with maternal and foetal imperatives.
Conditions unusually presenting in pregnancy include:
- Aortic dissection
- Spontaneous epidural haematoma
- Lumbar or sacral osteoporotic insufficiency fractures
- Infection, including TB
- Inflammatory spondylo-arthropathies
- Symptomatic vertebral haemangiomata
Pregnancy is a pro analgesic state with changes in endogenous opioids and increased pain thresholds. Usual advice is that anaglesics should be avoided in the first trimester if possible. Thereafter paracetamol is usually considered safe and benzodiazepines can be used for spasm. NSAIDs have been associated with an increase in miscarriage.
Codeine and other opioids can be taken. If taken just before delivery they may impact on the fetus’s breathing when delivered, although anecdotal reports have suggested these can be tolerated well by mother and foetus. Non-pharmacological options are gentle physiotherapy, TENS machines and acupuncture. We have undertaken epidural injections for disc prolapse and sciatica to avoid surgery on several occasions under ultrasound with good results.
Epidurals and spinal blocks for labour are usually safe in patients with back pain during pregnancy. If the mother is considered to have had significant disc pathology she should have a prenatal meeting with the obstetric and anaesthetic team to discuss a plan for this at the time of labour.
It is not possible to prevent all spinal pain in pregnancy. The risks may be mitigated by preconception attention to BMI, smoking and exercise. Most cases can be dealt with in a conservative manner with advice, reassurance and exercise with simple appropriate analgesia as required.
Serious pathology is rare but must be excluded. Investigation with MRI and treatment with therapeutic epidural injections or, in extremis, surgery is not absolutely contraindicated.
- Mr Fahy is a consultant spinal surgeon at Fortius Clinic and the Lister Hospital, London. Dr Towlerton is consultant in spinal and pain medicine at Fortius Clinic, and Chelsea and Westminster Hospital, London.
|Key learning points|
- Kouvacs FM, Garcia E, Royuela A, González L, Abraira V. Prevalence and factors associated with LBP and PGP in pregnancy. Spine 37; 17: 1516-33.
- Mogren IM, Pohjanen AI. Low Back Pain and Pelvic Pain during pregnancy. Spine 30; 8: 983-91.
- Smith MV, Marcus PS, Wurtz LD. Orthopaedic Issues in Pregnancy. Obstetrical and Gynaecological Survey 2008; 63; 2: 103-11.
- Wang PI, Chong ST, Kielar AZ et al. Imaging of pregnant and lactating patients: Part I, Evidence Based Review and Recommendations. AJR 2012; 198: 778-84.
- Brown MD, Levi AD. Surgery for Lumbar Disc Herniation During Pregnancy. Spine; 26: 4: 440-43.