Low back pain, sacroiliac pain and sciatic pain are common during pregnancy, affecting between 50% and 90% of women. Symptoms vary from mild ‘normal’ backache to severe pain that may render the woman bed-bound and necessitate early delivery.
The prevalence of low back pain during pregnancy increases with increasing maternal age. Numerous other risk factors have been investigated, but reports are contradictory about the relevance of maternal weight, socioeconomic class, number of pregnancies and previous history of back pain, although it is thought that women with a previous history of spinal surgery are not necessarily at increased risk of back pain during pregnancy.
Retrospective studies significantly under-report low back pain, usually quoting an incidence of 20-25%. This accounts for the conflicting data concerning any putative relationship between epidural analgesia and backache, which is now considered not to be causal (see Chapter 50, Backache).
Problems and special considerations
Non-specific back pain
The majority of back pain in pregnancy is directly attributable to the physiological changes that occur. The influence of relaxin, which is produced by the corpus luteum, leads to generalised ligamentous laxity. Serum levels of relaxin are highest during the first trimester of pregnancy. The pelvis widens, which may lead to sacroiliac joint instability. This may in turn allow anterior displacement of the sacrum, causing stretching of the lumbosacral plexus and subsequent pain. The expanding uterus alters the woman’s centre of gravity and causes an increased lumbar lordosis and pelvic tilt, and this, combined with the additional weight carried as pregnancy progresses, contributes to development of back pain. Some women complain of night-time back pain, for which a vascular mechanism has been proposed. It is suggested that inferior vena caval compression and increased intravascular volume occurring during recumbency may lead to distension in the vertebral venous plexus and subsequent stagnant hypoxia in the nerve roots and vertebral bodies, producing radicular and low back pain.
Pelvic girdle pain
Some women have symptoms relating specifically to the sacroiliac joints or the symphysis pubis. These women complain of pain localised to the pelvis and pubic symphysis, with radiation to the buttocks and thighs but not to the calf or foot, and commonly complain of pain when turning over in bed at night. In extreme cases there may be separation of the pubic symphysis, in which case the woman may become unable to walk or weight bear at all.
Abduction of the legs and external rotation of the hips may be difficult, and women may have anxieties about their ability to cope with labour and vaginal delivery. Pelvic girdle pain may persist for up to 2 years after delivery and has an increased incidence in future pregnancies.
Acute disc prolapse
Central disc herniation occurs in about 1 in 10,000 pregnancies and may require surgical decompression. Large central disc herniations can occur during pregnancy and at the time of delivery, and if there is an associated significant neurological deficit, surgical decompression is indicated. If magnetic resonance imaging (MRI) is used, disc bulges and herniations can be demonstrated in approximately half of all pregnant women, which is the same incidence as in asymptomatic non-pregnant women. Low back pain with sciatic radiation is common in pregnancy, and careful history taking and examination are needed to ensure that the availability of MRI does not lead to unnecessary surgical intervention.
Other causes
Less common causes of back pain should not be overlooked. Spinal cord tumours are extremely rare, and most of those reported during pregnancy are angiomas, presumed to be present before pregnancy. The increased vascularity of pregnancy is assumed to cause the tumours to become symptomatic. Secondary metastasis to the spine of primary malignancies such as breast can occur during pregnancy.
Management options
General management
Back care advice early in pregnancy has been reported to reduce the incidence and severity of low back pain during pregnancy. This may be particularly important for women with a history of pre-pregnancy back pain, who may be at increased risk of worsening pain during pregnancy. Simple physiotherapy, exercise programmes and the use of lumbosacral corsets have all been reported to provide symptomatic pain relief during pregnancy, although evidence for treatment of pelvic pain is less clear.
Simple analgesics such as paracetamol and codeine-based preparations are acceptable during pregnancy, but non-steroidal anti-inflammatory drugs should be avoided whenever possible. If their use is considered essential, treatment should be agreed with the obstetrician, and fetal cardiac ultrasound monitoring arranged because of the risk of premature closure of the ductus arteriosus. Amitriptyline may be prescribed as a co-analgesic, especially if pain is disrupting normal sleep patterns. In cases of severe back pain, strong opioid analgesia may be required.
Transcutaneous electrical nerve stimulation for back pain during the second half of pregnancy is not recommended by the manufacturers of the machines but is used in clinical practice, frequently with good effect. Injection of local anaesthetic and steroid into the epidural space, the sacroiliac joints or the symphysis pubis may be considered necessary if symptomatic control of pain cannot be achieved by other methods. The safety of such procedures during pregnancy is unknown, and a risk-benefit analysis must be undertaken for each woman.
Delivery before term may be considered when pain control is difficult to achieve.
Anaesthetic management
Women with pre-existing musculoskeletal pathology should be fully assessed during the antenatal period. Previous spinal surgery is not a contraindication to regional analgesia and anaesthesia, although women may have been told by their midwife, general practitioner or orthopaedic surgeon that they will be unable to have epidural analgesia (see Chapter 115, Kyphoscoliosis). There may be respiratory impairment following significant corrective surgery, and some postoperative neurological deficit, and if so these must be documented antenatally. Women should be told that epidural analgesia for labour does not increase the likelihood of experiencing postnatal backache. If neuraxial analgesia/anaesthesia is administered, both the obstetric team and patient must be careful not to over-extend relaxed joints or adopt positions that would not have been accepted before analgesia/anaesthesia.
Regional anaesthesia and analgesia in women who have had discectomy or laminectomy is not usually technically difficult, but there may be a slightly increased risk of accidental dural puncture or poor spread of local anaesthetic, and patients should be warned about this. There is some evidence to suggest that women with severe chronic back pain with associated neurology may have a delayed onset of epidural analgesia. This may be due to increased time for diffusion of local anaesthetic to the affected nerve root because of scarring that develops secondary to disc injury, or mechanical obstruction by disc prolapse.
There is no contraindication to vaginal delivery, nor to the use of regional analgesia in women with pregnancy-related back pain, although many women request (and some obstetricians suggest) delivery by elective caesarean section to avoid any risk of exacerbating existing back symptoms.
The management of women who have had surgery is considered in Chapter 115, Kyphoscoliosis.
Key points
• Low back pain is common in pregnancy; it is usually mechanical and should be treated symptomatically.
• Although rare, acute disc prolapse with neurological deficit may occur and require surgical treatment.
• There is no contraindication to epidural or spinal analgesia or anaesthesia in women with low back pain.
• Serious spinal and neurological pathology may, rarely, present during pregnancy, and should always be considered in the differential diagnosis of new-onset back pain.
Further reading
Liddle SD, Pennick V. Interventions for preventing and treating low-back and pelvic pain during pregnancy. Cochrane Database Syst Rev 2015; (9): CD001139
Orlikowski CE, Dickinson JE, Paech MJ, McDonald SJ, Nathan E. Intrapartum analgesia and its association with post-partum back pain and headache in nulliparous women. Aust N Z J Obstet Gynaecol 2006; 46: 395-401.
Vermani E, Mittal R, Weeks A. Pelvic girdle pain and low back pain in pregnancy: a review. Pain Pract 2010; 10: 60-71.