When a woman becomes pregnant her body undergoes tremendous change hormonally and anatomically which may cause musculoskeletal complaints or alter the course of preexisting ailments. Retrospective reviews reveal that almost all women have some musculoskeletal complaint during their pregnancy.11,31,32,36,47 The population is becoming increasingly aware of the benefits of exercise and a healthy lifestyle. Many women wish to continue with their exercise regimens throughout their pregnancies and it is important for the physician to understand the effects of exercise on the mother and her unborn child. There is evidence that women who are fit before becoming pregnant and continue their exercise programs throughout their pregnancies have a decreased incidence of musculoskeletal complaints.54 The physiologic changes in the cardiovascular and pulmonary systems also must be understood when counseling patients on exercise during pregnancy.
Some, but not all of the effects of estrogen, relaxin, and prolactin on the musculoskeletal system are known; however, more research must be done on women who are pregnant and those who are not. In addition to the effects of hormones on the musculoskeletal system, other effects of pregnancy, such as weight gain, cardiovascular changes, pulmonary changes, and edema can cause musculoskeletal complaints. Common complaints during pregnancy include low back pain, sacroiliac joint pain, carpal tunnel syndrome, de Quervain's stenosing tenosynovitis, and pelvic pain. The more common complaints of pregnancy are summarized in Table 1. Pregnancy also can affect preexisting musculoskeletal conditions such as rheumatoid arthritis and ankylosing spondylitis. Studies have been done on the effects of pregnancy on these disorders as well as scoliosis and women with previous spinal cord injuries.6,29,32,33,35,39,52,53,56,57
THE CHANGES OF PREGNANCY
The Musculoskeletal System
Many of the effects of hormones on the musculoskeletal system have yet to be elucidated in pregnant and nonpregnant women. The hormone relaxin has been identified as being responsible for allowing increased joint laxity during pregnancy and levels of relaxin are highest in the third trimester.62 Relaxin allows the joints of the pelvis to become more flexible for the fetus to pass.42 Relaxin also has a direct affect on collagen remodeling.65 In addition to relaxin, progesterone also contributes to increased joint laxity during pregnancy.17 A study by MacLennan et al46 showed that the serum level of relaxin in women who are incapacitated by pelvic pain during pregnancy is significantly higher than those women who do not have pelvic pain. Serum levels return to near normal levels in both groups by the third postpartum day.46 It recently has been hypothesized that relaxin in athletes who are not pregnant may contribute to the increased rates of anterior cruciate ligament tears in females compared with males; however, this has yet to be proven.3
Estrogen and progesterone receptors have been identified on human fibroblasts in anterior cruciate ligaments, synoviocytes in synovial lining, and in cells in the blood vessel walls of anterior cruciate ligaments.4,44 The exact function of these receptors is unknown; however, it has been shown that at increasing local estradiol concentrations, collagen synthesis is significantly reduced in rabbits.43 In a recent study in which anterior cruciate ligament tears in females were tracked, an attempt was made to correlate phase of cycle and incidence of anterior cruciate ligament tears. A statistically significant number of anterior cruciate ligament tears were found during the ovulatory phase of the cycle when estrogen levels are highest.65 Although there were several limitations to this study, one can extrapolate from these data that pregnant women may be at increased risk for ligamentous injury because of increased estrogen and relaxin levels.
Attempts have been made to track the effects of pregnancy on bone through various methods and with varying results. In a 1995 study by Matsumoto et al,49 dual energy xray absorptiometry was used to quantify the bone mineral density of the distal radius in women during pregnancy and lactation. No noticeable change was found in bone mineral density during pregnancy, or in women who were not breastfeeding. Women who breast fed had a significant decrease in bone mineral density at 1, 3, and 6 months postpartum with a continued decrease at 12 months postpartum.49 In a 1996 study by Yamaga et al,66 ultrasound and biochemical markers were used to determine changes in bone mass and bone turnover during pregnancy and the puerperium. Their study showed that there is increased bone formation and bone resorption during the third trimester of pregnancy and the puerperium. They also showed that women who breastfeed continue to have higher bone metabolism; however, this was not significantly increased over women who did not breastfeed and did not affect bone mass.66 The varying results of these recent studies49,66 and of those of previous studies1,12,13,19,20,30,41,60,61 only underscore the lack of understanding of the effects of pregnancy on maternal bone mass. The incidence of idiopathic osteoporosis associated with pregnancy probably is greater than the current literature suggests.66
Weight Gain and Edema
Most of the weight gained during pregnancy is caused by the enlarging uterus, fetus, and breasts, and the increased blood volume, extravasation of extracellular fluid, and water retention. On average, a woman will gain approximately 11 kg during pregnancy.15 During the late phase of pregnancy the average woman retains approximately 6.5 L of fluid which may increase by 1 L at the end of the day resulting in pitting edema. This increase is caused by an increase in venous pressure below the uterus as the gravid uterus puts pressure on the vena cava.15 The gravid uterus moves the center of gravity forward and increases stress on the lumbar spine and abdominal musculature. The weight gain of pregnancy increases load bearing and should result in positive bone mineralization; however, the demands for calcium by the fetus apparently negate the effect of increased load bearing by the mother.66
The Cardiovascular and Pulmonary Systems
During pregnancy plasma volume increases 40% to 90%38 and blood volume increases on average 45% of normal to meet the demands of the enlarged uterus and to protect the mother and fetus from the effects of impaired venous return during pregnancy. The increased blood volume also serves to protect the mother from blood loss during the birth process. This increase varies significantly among women.15 Despite the increased blood volume the concentration of hematocrit and erythrocytes decrease slightly during pregnancy.15
The mother's heart rate at rest increases 10 to 15 beats per minute during pregnancy. As the uterus enlarges and displaces the diaphragm superiorly, it also displaces the heart superiorly and to the left, rotating on its axis.15 Cardiac output increases throughout pregnancy and is affected by the position of the mother.15,38 After the first trimester, when the mother lays in a supine position there is obstruction of venous flow and a resultant decrease in cardiac output which may cause symptoms of hypotension. During the third trimester, when the mother lays in the left or right lateral recumbent position, cardiac output is maximal. Prolonged motionless standing will produce a decrease in cardiac output and should be avoided.2
In addition to affecting the position of the heart, the upward displacement of the diaphragm by the uterus affects lung volume. Although the subcostal angle widens, the transverse diameter of the thoracic cage increases approximately 2 cm and the circumference increases by 6 cm. This increase is not large enough to prevent a decrease in lung volume attributable to the elevated diaphragm. Diaphragmatic excursion is increased during pregnancy and therefore tidal volume increases.15 Ventilation increases from approximately 7 L/minute to approximately 10 L/minute.38 As gestational age increases there is an increase in resting maternal oxygen consumption to 16% to 32% above reported values for women who are not pregnant.45 Because resting oxygen requirements are increased during pregnancy, there is decreased oxygen available for exercise and therefore women exercising during pregnancy must adjust their exercise intensity.2
Exercise During Pregnancy
As society becomes more active and a greater proportion of the population engages in regular exercise, correspondingly a greater number of women who become pregnant will want to continue with their exercise programs. Multiple studies have been done to assess the effects of exercise on the mother and fetus.2,14,16,18,24,27,34,38,45,50,56 It seems that expectant mothers who participate in moderate exercise on a regular basis are likely to have an improved course of pregnancy compared with those mothers who remain sedentary during their pregnancies.24,34 One of the biggest concerns regarding exercise during pregnancy is hyperthermia. Hyperthermia increases oxygen demands and in early pregnancy may be associated with neural tube defects.16,18 Women who are fit before pregnancy tend to thermoregulate more efficiently than women who were not fit before conception and begin an exercise program during pregnancy.2 The redistribution of cardiac output during exercise will affect uterine blood flow; however, whether this redistribution is enough to affect the fetus is unknown.34
Clapp14 studied women who were physically fit before conception and who continued to exercise during their pregnancies and compared them with women who stopped their regular exercise program before the end of the first trimester. He found that there was a decreased incidence of operative delivery and fetal stress in the group of women who exercised compared with the women who did not exercise. He also found that women who exercised had an earlier onset of labor and that birth weight was reduced. The difference in birth weight seemed to be a result of decreased fetal fat mass.14 In a similar study Hall and Kaufmann27 evaluated the effects of aerobic and strength conditioning on pregnancy outcomes. They, too, found more favorable outcomes in the women who continued to exercise during their pregnancies. Dale et al16 performed a similar study with runners. Their data indicated no significant differences between women who ran and women who did not run in the categories of weight gain during pregnancy, length of labor, and incidence of obstetric complication. Birth weights essentially were identical between the two groups studied.
When advising a woman on a pregnancy exercise protocol one must assess her level of physical fitness and level of activity before conception. Contact sports and supine exercise should be discouraged.34 Hyperthermia is a concern as is unrecognized fetal hypoxia during exercise. Weight lifting programs should be supervised to help the woman adjust techniques as her body changes during her pregnancy.27 The recommendations of the American College of Obstetricians and Gynecologists regarding exercise during pregnancy are summarized in Table 2 and contraindications to exercise during pregnancy are summarized in Table 3.2
Common Musculoskeletal Complaints During Pregnancy
Back pain is one of the most common musculoskeletal complaints during pregnancy and most women expect to have some discomfort in their back during pregnancy.22 Estimates of incidence of back pain are approximately 50% to 70%.11,33 Women who have a previous history of back pain are more likely to complain of back pain during pregnancy and the pain is more likely to be of longer duration. Women who have had back pain during a previous pregnancy are at increased risk for back pain during a subsequent pregnancy and the pain is likely to be more severe.54 Ostgaard and Andersson54 found increased incidence of back pain in younger women whereas Mantle et al47 found an increased incidence of back pain in older women. Increasingly parity is associated with increased incidence of back pain during pregnancy.47 There seems to be no association between back pain during pregnancy and weight gain during pregnancy, obesity before pregnancy, height, or birth weight.47 Incidence of herniated disc resulting in radiculopathy during pregnancy is no greater than that for the general population.31 LaBan et al40 estimated the incidence of herniated lumbar disc during pregnancy at 1:10,000.
The increased lordosis of pregnancy combined with the effects of relaxin on the joints of the pelvis and the weight of the gravid uterus with resultant anterior shift in the center of gravity all contribute to complaints of low back pain in the patient who is pregnant.25 As the pregnancy progresses and the size of the uterus increases with the changes noted above, the muscles of the low back must assume much of the work to maintain an upright posture as the abdominal muscles and ligaments of the pelvis stretch.36
Treatment of low back pain in a woman who is pregnant consists of a program stressing correct posture, pelvic tilt, and strengthening of the abdominal and lumbar musculature positioning, use of a brace, rest, and acetaminophen. The majority of women will respond to this conservative regimen. Women who are physically fit before becoming pregnant seem to have fewer musculoskeletal complaints.33,55 A physical therapy and education program reduced sick leave time and reduced back pain in patients reported in a study by Ostgaard et al.55 Some women find lumbosacral supports helpful in reducing back pain during pregnancy. Nonradicular back pain typically will resolve within 6 weeks of delivery.33
Although the incidence of herniated lumbar disc is no greater for pregnant women than for women who are not pregnant, for those women who herniate a disc during pregnancy, the issue of the effects of the condition for mother and baby must be considered. Surgical intervention during pregnancy is reserved for women with bladder or bowel dysfunction or both.33 Pregnant women who have radiculopathy and do not have bladder or bowel dysfunction are treated in much the same way as pregnant women with back pain without a radiculopathy.40 Acetaminophen is a safe drug during pregnancy and is prescribed commonly for pain.10 Methocarbamol can be used for severe muscle spasms and does not seem to be teratogenic.8,10 Codeine is a category C drug that is not associated with fetal malformations; however, there is a risk of fetal withdrawal syndrome if the mother takes large amounts of codeine at the end of pregnancy.8,10 Propoxyphene also is a category C drug for which there has not been a clear association of fetal malformations. However, case reports of withdrawal syndrome have been associated with its use during pregnancy.10
Cesarean section is the delivery method of choice for women with a herniated disc during pregnancy to avoid increased intrathecal pressures during labor.40 Radicular pain frequently is diminished after delivery; however, many women eventually undergo excision of their herniated disc once they have given birth.40
As previously stated, relaxin and progesterone allow the joints of the pelvis to become more flexible during pregnancy as the mother's body prepares for the delivery of the baby.17,26 This increased laxity may cause pain in the sacroiliac joint or at the pubic symphysis in some women. Increased levels of relaxin have been reported in women who have incapacitating pain over those women without pain.46 Changes in the width of the pubic symphysis probably occurs in all pregnant women and the maximum widening which is considered nonpathologic is 10 mm.17,42
There have been several case reports of rupture of the pubic symphysis.17,42 Etiologic factors of rupture of the pubic symphysis are hard precipitous labor, difficult forceps delivery, cephalopelvic disproportion, abnormal presentation, multiparity, trauma caused by excessive or forceful abduction of the thighs during delivery, previous pelvic trauma, or preexisting bony abnormality (Table 4). The reported incidence of rupture of the pubic symphysis varies and seems to be decreasing as the number of forceps deliveries decreases.17,42 Treatment usually is nonoperative and consists of reduction and tight pelvic binding and rest in a decubitus position. External fixation can be used for those patients who have inadequate reduction, recurrent diastasis, or persistent pain.17,42
Posterior pelvis pain during pregnancy should be distinguished from lumbar back pain. Ostgaard and Andersson54 studied back and posterior pelvic pain and found that women with posterior pelvic pain were more likely to have relief of pain with use of a nonelastic sacroiliac belt than women with lumbar back pain. They also found that in women with posterior pelvic pain, back strengthening exercises tended to worsen their symptoms. Some women suffer from lumbar and posterior pelvic pain; however, if a distinction can be made it may help to better direct treatment.54
Transient Osteoporosis of the Hip
Transient osteoporosis is a rare syndrome of unknown etiology which is seen most commonly in the hip although any joint may be involved. The syndrome occurs most commonly in pregnant women in their third trimester and men in their forties. The typical presentation in these patients is of severe hip pain without a history of trauma. The pain may be of insidious or acute onset, and the patient does not have a history of illness. The area of greatest pain usually is over the groin and greater trochanter and radiating into the anterior thigh. The patient has an antalgic gait and increased pain with weightbearing.7
The diagnosis of transient osteoporosis is based on clinical presentation, a negative result of a hip aspirate, and radiographic findings. The radiographic findings typical of transient osteoporosis are osteopenia of the involved bone with indistinctness of the subchondral bone and preservation of the joint space.5,7,9 The diagnosis usually can be made by obtaining one anteroposterior (AP) radiograph of the patient's pelvis. With properly positioned lead shielding, the risk to the fetus is minimal and should outweigh the potential complication of femoral neck fracture and the resulting complications that may occur with this injury.9 Magnetic resonance imaging (MRI) will show decreased signal on T1-weighted images and increased signal on T2-weighted images.33 The safety of MRI during pregnancy has not yet been defined.48 No laboratory studies have been found to be diagnostic of this disorder. Erythrocyte sedimentation rate and urinary hydroxyproline levels are elevated in some patients with transient osteoporosis of the hip; however, these levels are normally elevated in late pregnancy and therefore their clinical usefulness is negated.7
Treatment of transient osteoporosis of the hip is conservative and consists of protected weightbearing for pain relief and reduction of fracture risk. Women in the third trimester of pregnancy who have groin and thigh pain should have the presumed diagnosis of impending or actual stress fracture. Physical therapy is recommended to maintain range of motion (ROM) and to prevent joint contractures. If fracture occurs operative intervention is required to avoid the potential complications of avascular necrosis and osteoarthritis.5,7,9
De Quervain's Disease
De Quervain's disease is a stenosing tenosynovitis of the first dorsal compartment of the wrist that may occur during late pregnancy and lactation. The tendons of the extensor pollicis brevis and the abductor pollicis longus become inflamed within their sheath as they pass over the radial styloid. Patients typically present with radial sided wrist pain with increased pain on radial and ulnar deviation of the wrist. There sometimes is localized swelling over the involved compartment and tenderness over this area.51,58,59 In 1930 Finkelstein23 described a test for de Quervain's syndrome. The patient places the thumb in the closed fist and the wrist is ulnarly deviated, a maneuver that reproduces the patients symptoms.23 De Quervain's disease is caused by repetitive trauma involving radial and ulnar deviation of the wrist. Infant care activities seem to exacerbate the condition.58 It has been theorized that the edema of pregnancy may contribute to this problem.33 Prolactin also has been suggested as a possible contributory factor37 as have relaxin and progesterone.58
Treatment of de Quervain's syndrome in the patient who is pregnant or lactating is conservative and consists of the use of a splint.51 A thumb spica splint leaving the interphalangeal joint free and placing the metacarpophalangeal joints in slight abduction and extension is prescribed.33 Local injection of the first dorsal compartment with steroid and local anesthetic can be done.58 Nonsteroidal antiinflammatory drugs should be used with caution in women who are pregnant or lactating and have de Quervain's disease. Once breastfeeding has been discontinued, symptoms usually will resolve quickly. Few women require surgical intervention for this problem.37
Carpal Tunnel Syndrome
Carpal tunnel syndrome is recognized as a common complication of pregnancy whose incidence has been reported between 1% and 25%.51,64 It is more common in older primiparas with generalized edema.16 It also is more common in women suffering from preeclampsia and hypertension. Women who have carpal tunnel syndrome during one pregnancy are at increased risk for having the syndrome during subsequent pregnancies and later in life.33 Prolactin and relaxin have been suggested as possibly being contributory to carpal tunnel syndrome in women who are pregnant.51 Onset of symptoms usually occurs in the second or third trimester and consists of numbness and tingling into the median nerve distribution of the hand and night pain.33,64
Carpal tunnel syndrome found in association with pregnancy almost always resolves after delivery. Most women have complete resolution of symptoms within 4 weeks of giving birth.33 Symptoms tend to continue in women who breastfeed their infants and resolve once breastfeeding is discontinued. For this reason treatment continues to be conservative and consists mainly of the use of a splint.63 Local steroid injection or oral diuretics also have been used in patients with recalcitrant symptoms. Surgical intervention rarely is indicated.21
Leg cramps are another common musculoskeletal complaint during pregnancy affecting between 15% and 30% of women. These cramps usually occur during the second half of pregnancy, most often affecting the muscles of the calf and occurring at night approximately 75% of the time.28 The cramps are described as forceful tetanic contractions that often wake the woman from a sound sleep. The exact etiology of leg cramps during pregnancy is unknown but they may be caused by a magnesium or calcium deficiency.33 Hammar et al28 reported that there was a clinical improvement in pregnant women who had leg cramps after calcium supplementation thereby supporting the hypothesis that decreased calcium may be responsible for the cramps.
Effects of Pregnancy on Preexisting Musculoskeletal Conditions
Concerns that pregnancy may cause scoliotic curves to progress prompted a study by Betz et al6 who observed curves in patients who were skeletally mature. Some of these patients became pregnant and some patients did not become pregnant. They found that pregnant women with scoliosis were no more likely to have progression of their curve than their counterparts who did not become pregnant. Risk of curve progression was not influenced by maternal age at first pregnancy, presence of pseudarthrosis, or stability of the curve at time of pregnancy. Incidence of Cesarean section was 1/2 the national average and no Cesarean sections were done because of the scoliosis. The only problems during delivery related to the curve were encountered in the administration of spinal anesthesia. Betz et al6 concluded that spinal curves in adults with scoliosis do tend to progress; however, the progression does not seem to be influenced by pregnancy.6
Spondylolisthesis and Spondylolysis
During a 20-year period, Saraste57 observed, men, women who were not pregnant, and women who had been pregnant and made comparisons with respect to degree of spondylolisthesis, its subsequent progression, functional impairment, and occurrence and intensity of low back symptoms. No difference between the groups could be found nor was spondylolysis with or without spondylolisthesis a risk for pregnancy complications. In a similar study, Sanderson and Fraser56 studied men, nulliparous women, and women who had been pregnant who had degenerative spondylolisthesis at the L4-L5 level and found that women who had children had a significantly higher incidence of degenerative spondylolisthesis.
In a retrospective review of patients with ankylosing spondylitis, Ostensen52 and Ostensen et al53 found that the course of the disease is largely unaffected by pregnancy. Half of the patients had no change in their symptoms, 24% experienced exacerbation of symptoms, and 20% reported remission of symptoms. Women who report a remission of symptoms will have some other disease process such as psoriasis, ulcerative colitis, or small joint arthritis. The outcome of pregnancies in women suffering from ankylosing spondylitis is not different from the general population.53 A postpartum flare up of the disease occurred in approximately 90% of women.52
Rheumatoid Arthritis and Juvenile Rheumatoid Arthritis
Pregnancy causes a remission of rheumatoid arthritis in approximately 2/3 of women with the disease who become pregnant. The remission continues until approximately 6 weeks after delivery after which time the patient may have an arthritic flare up.33 The exact etiology of this remission is unknown; however, investigators have proposed that elevated levels of alpha glycoprotein, which decreases inflammation by suppressing monocytes, may be responsible.33 The pregnancy serum has an inhibitory effect on phagocytosis, chemotaxis, lymphocyte transformation, and mixed lymphocyte reactions.39 It also has been hypothesized that the fetus may have an influence on autoimmune disease. The fetal suppressor cells that prevent rejection of the fetus by the mother may be responsible.33
Approximately 60% of women with active juvenile rheumatoid arthritis have a remission during pregnancy. If the arthritis is in remission, the disease is not reactivated. The sequelae of juvenile rheumatoid arthritis is a frequent reason for Cesarean section. Fifty percent of women with juvenile rheumatoid arthritis will experience a flare up in the postpartum period.52
Although many women with rheumatoid arthritis experience a decrease in their symptoms during pregnancy, treatment of the disease still may be necessary. As stated previously, propoxyphene and codeine, both Category C drugs, have no definite association with fetal malformations; however, they may cause neonatal withdrawal syndrome. Acetaminophen seems to be a safe drug during pregnancy.10 Ibuprofen, naproxen, fenoprofen, and ketoprofen have not been shown to have significant teratogenic effects in humans or animals; however, there is a theoretical risk of closing of the ductus arteriosus with nonsteroidal antiinflammatory use during pregnancy.10 The nonsteroidal antiinflammatory drugs also may delay labor and should be given with caution. Use of nonsteroidal antiinflammatory drugs after the twenty-fourth week of pregnancy is not recommended. When given at normal therapeutic doses, corticosteroids do not seem to have a significant incidence of teratogenic effects. Gold therapy may be continued and does not seem to have any adverse effects on the fetus.10 With any drug treatment the risk to the fetus that the drug poses must be weighed against the effects the untreated disease will have on the mother and her ability to carry the pregnancy to term.
Systemic Lupus Erythematosus
In women who suffer from systemic lupus erythematosus, the question of whether pregnancy causes exacerbations or remissions of the disease has yet to be answered because of difficulties in distinguishing between preeclampsia and a flare up of the disease. Women who are in clinical remission at conception seem to have fewer complications than women with active disease. There is a 30% to 50% complication rate in women with inactive disease at conception. Fetal survival is 85% to 90% in several reported case series after exclusion of spontaneous abortions during the first trimester.29,32 Some fetal wastage and maternal complications may be related to anticardiolipin antibodies.29
Patients With Spinal Cord Injuries
Many women with spinal cord injuries can become pregnant. Most of these women can have normal vaginal deliveries; however, they may not be able to feel contractions or the onset of labor. If the lesion is below T-12, sensation should be intact and contractions should be felt normally. When the lesion is above T-10 the contractions will be poorly felt. If the lesion is above T5 voluntary use of the abdominal muscles is absent.35
Patients with lesions above T7 carry a risk of autonomic dysreflexia. This occurs when the autonomic system is stimulated and remains uninhibited. Autonomic dysreflexia may occur in response to contractions, vaginal examination, a distended bladder, or a urinary tract infection. The syndrome can be manifested by hypertension, sweating, anxiety, or cardiac abnormalities and can be severe enough to be life-threatening. In patients with autonomic dysreflexia, the noxious stimulus is removed and hypertension and cardiac problems are treated. Epidural anesthesia will control autonomic dysreflexia and it usually will subside once the baby has been delivered.33,35
There are several musculoskeletal conditions that can be caused or exacerbated by pregnancy. In the majority of patients these problems can be treated in a safe and effective manner for mother and fetus. Knowledge of the effects of pregnancy on the musculoskeletal system will help the practitioner be able to treat these problems better, counsel women with preexisting conditions that may be altered by pregnancy, and counsel women regarding a safe exercise program during pregnancy.
The authors thank James W. Akin, MD, Robert J. Homm, MD, Jesse Pace, and Carolyn Large for their assistance in the preparation of this manuscript.
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