Management of Prenatal Low Back Pain
It is estimated that 25% of pregnant women will experience, at least temporarily, some disability related to musculoskeletal pain.1 Pregnancy-related back pain may result in sleep disturbances and may affect the quality of life for these patients.2-4 The good news is that there are a number of management options to ease back pain—including tips from the American College of Obstetricians and Gynecologists (ACOG), exercises, acupuncture, medications, and osteopathic manipulative treatment (OMT). It has been shown that the use of OMT during the third trimester of pregnancy has clinical benefits in improving back pain and minimizing the decline in functioning associated with low back pain. This article will review the use of osteopathic treatment in pregnant patients.
Musculoskeletal Changes During Pregnancy
During pregnancy, there are normal physiological changes that occur in response to weight gain and hormonal changes. On average, pregnant women may gain 25 to 35 pounds.5 This can cause the force across some joints to increase up to two-fold.2 Additionally, because the enlarged uterus causes a change in the patient’s center of gravity, her spine needs to compensate. In order to do so, there will be an exaggerated lordosis of the lower back, forward flexion of the neck, and downward movement of the shoulders.5 The abdominal muscles help to support the core. Weakness and stretching of these muscles will put more strain on the paraspinal muscles affecting the patient’s posture as well.5
Changes in the pelvis and sacrum may be construed as low back pain. In order to prepare for delivery of the fetus, there is a widening and increased mobility of the sacroiliac joints and pubic symphysis.5 There is a significant increase in the anterior tilt of the pelvis, where greater use of the hip extensors, abductors, and ankle plantar flexor muscles is required.6 Furthermore, stance is widened in order to maintain stability of the trunk during movement.3
Hormonal changes during pregnancy also have musculoskeletal consequences. Relaxin is a hormone produced by the corpus luteum, decidua, and placenta. Its concentration peaks during the first trimester to assist placental implantation and growth. Then later in pregnancy, relaxin contributes to separation of the pubic symphysis, relaxation of the myometrium, and softening of the cervix.4 It has been thought that the release of relaxin contributes to joint laxity in various ligaments. This may lead to some instability of the lumbar spine anterior and posterior longitudinal ligaments, leaving a patient susceptible to further lumbar strain. However, other factors may contribute to joint laxity of the extremities. In a study of 35 women, 19 women (54%) demonstrated a ≥10% increase in wrist laxity from the first to third trimester; however, the finding did not correlate to the levels of relaxin.7 Joint pain has been associated with increased estradiol and progesterone levels; thus, it could be possible these hormonal changes are contributory, although further research is needed.
Causes of Low Back Pain
In a survey of almost 1,000 pregnant women, 41% reported a first occurrence of back pain during pregnancy.8 However, back pain is more common in women who have had preexisting back pain, pain during a previous pregnancy, advanced maternal age, and multiparity.9
Most cases of back pain during pregnancy are due to mechanical factors from altered posture, muscle weakness, joint laxity, and/or vertebral facet joint irritation.9 Additionally, patients with preexisting degenerative spondylolisthesis may have aggravated symptoms during pregnancy, especially in the L4-L5 level of the lumbar spine.10 Despite common misconceptions, disc herniation is rarely a cause of low back pain in pregnancy.11 About 10% of nonpregnant women of childbearing age without back pain have asymptomatic disc herniation and about 40% have disc bulges that can be seen on magnetic resonance imaging.12 The incidence of these abnormalities, such as disc herniation, is similar in nulliparous nonpregnant, multiparous nonpregnant, and pregnant women.13 Therefore, disc herniation is not considered in the etiology of low back pain directly related to pregnancy.
When a pregnant patient presents with low back pain, one must consider both lumbar causes and pelvic or sacroiliac causes. This can be accomplished with a good history and physical examination. In general, back pain can present at any time during pregnancy, but is most prevalent in the second half and may be described as pain that is aggravated by activity and relieved with rest. The patient may state that the pain begins in the lower back and radiates down the posterior thighs or even the lower abdomen and anterior thighs.14 Physical examination can help to differentiate between lumbar and sacral origination of the pain. Lumbar pain is characterized by pain above the sacrum. It is accompanied with decreased range of motion at the lumbar spine and pain may be exaggerated with forward flexion at the waist.15 In contrast, sacroiliac pain is worse with extension and external rotation of the hip on the affected side. Pain may be elicited in the sacroiliac joint by the iliac compression test with the patient lying supine.15
Pelvic pain may present similar to low back pain and may originate from the pelvic girdle or secondary to pubic symphysis separation. Posterior pelvic girdle pain is related to the sacroiliac joints. It is described as a stabbing pain in the buttocks distal and lateral to L5-S1, may radiate down to the knee, and may be worse when weight bearing on the ipsilateral leg. This pain may be assessed with the posterior pelvic pain provocation test. This is done by having the patient lie supine, flex the hip to 90°, and exert pressure on the knee down towards the hip while stabilizing the pelvis with a hand on the contralateral anterior iliac spine.16
Whatever may be the cause of back pain during pregnancy, a number of treatment options are available varying from medical management, like acetaminophen and corticosteroid injections, to more conservative approaches including exercises for stretching and strengthening, physical therapy, acupuncture, mechanical bracing for stability, and OMT.