Low Back Pain in Pregnancy
By Dr Robert Gassin

Low back pain is a common complaint, reported by approximately 50% of pregnant women. Although rarely debilitating, it is one of the main reasons for sick leave during pregnancy. In our society, many women consider low back pain a normal consequence of being pregnant and either tolerate or self manage it.

Health professions have been slow to tackle the problem, and it is only recently that quality research has been undertaken. The perception that the problem is transient and will resolve once the pregnancy is over, the inability to use standard investigative measures such as X-ray and CT scan and the reluctance to use pharmacological agents during pregnancy, have been barriers to research.

Classification
The use of differing terminology makes interpretation of research findings difficult. There is growing consensus that what is normally referred to as low back pain in pregnancy can be subdivided into low back pain (LBP) and posterior pelvic pain (PPP). This division is important in terms of both management and prognosis.

LBP refers to pain experienced predominantly in the region bounded:

• Superiorly by an imaginary line through the inferior margin of the last thoracic spinous process.
• Inferiorly by an imaginary line through the posterior sacrococcygeal joint.
• Superolaterally by vertical lines tangential to the lateral borders of the lumbar erector spinae and inferolaterally by imaginary lines passing through the posterior superior and posterior inferior iliac spines.

In most instances, its aetiology is the same as that of LBP in non-pregnant individuals.

PPP is thought to arise from the pelvic joints and is defined by its diagnostic criteria:

• A history of time and weight-bearing related pain in the posterior pelvis, deep in the gluteal area.
• A pain drawing with well defined markings of stabbing in the buttocks distal and lateral to the L5-S1 area, with or without radiation to the posterior thigh or knee, but not into the foot.
• A positive ‘posterior pelvic pain provocation test’.
• Free movement in the hips and spine and no nerve root syndrome.
• Pain when turning in bed.

When compared to women with LBP, those with PPP:

• Have higher pain intensity,
• Are more disabled,
• Are more difficult to treat successfully,
• Have a worse prognosis.

Differential Diagnosis
Although the cause of low back pain in pregnancy is benign in the vast majority of cases, on rare occasions, serious medical conditions such as miscarriage, infective sacroiliitis, discitis, intra-abdominal pathology, tumours and pathlogical vertebral fractures have all been reported. When assessing a pregnant patient presenting with low back pain, it is essential for the clinician to exclude these conditions. This is best achieved by a thorough medical history and physical examination with an emphasis on excluding red flags (see list below).

1. Unremitting pain
2. Neurological symptoms and signs
3. Use of corticosteroids
4. Temperature > 37.8ºC
5. Consitutional Symptoms
6. Weight loss
7. Past history of cancer
8. Urinary symptoms
9. Abdominal pain
   • Cramps
   • Constant
10. Vaginal bleeding /discharge
11. Trauma

Risk Factors
The single greatest risk factor for the development of low-back pain in pregnancy, is a history of low-back pain prior to pregnancy. This includes low-back pain prior to the present pregnancy, before the first pregnancy and during previous pregnancies. A previous history of low-back pain accounts for 40% of low-back pain during pregnancy and a woman with a history of back pain has a 2.09 times higher risk of developing back pain in a future pregnancy. Furthermore, a history of previous low back pain increases the likelihood of suffering more intense and longer lasting back pain in pregnancy.
Other risk factors include: low socioeconomic class, BMI prior to pregnancy, large transverse and/or sagittal abdominal diameter, pronounced lumbar lordosis prior to pregnancy, multiparity, race, scoliosis and belief about how strong the back is. These are each minor contributing factors.

Management
Over recent years, several treatment modalities for LBP and PPP in pregnancy have been investigated.

Exercise in hot water for 1hr/wk during the 2nd half of pregnancy has been found to be superior to exercise and relaxation for LBP. Significantly more women in the water gymnastics group were painfree at weeks 31 and 33-38 and there was less sick leave in this group after weeks 32-33.

Several small, poor quality studies have shown spinal manual therapy including mobilisation and manipulation to give short-term pain relief in the management of LBP/PPP.

There is no evidence in support of he effectiveness of exercise or physical activity in the management of LBP or PPP.

A sacroiliac belt has been shown to increase walking distance but has no impact on pain at rest or with activity and does not reduce sick leave.

A single, poor quality study, demonstrated more improvement in LBP and disability with acupuncture than physiotherapy.

A Wedge shaped pillow used to support the abdomen whilst lying on the side has been shown to be effective at alleviating LBP and back pain related insomnia in 36 weeks pregnant women.

As well as the above treatment modalities, education regarding the nature of LBP and/or PPP, reassurance that the condition is benign and the following back care advice are deemed safe and potentially beneficial.

• Wear comfortable soft-soled shoes or insoles.
• Take small steps.
• Sit with small cushion in small of back.
• Lie on the side with a cushion between the knees and ankles and the abdomen supported by a pillow.
• Have short periods of rest combined with activity.
• Use ice or heat on the painful area.
• Have a massage.
• Use paracetamol with or without low dose codeine as required.