Department of Orthopedic Surgery, Saint Louis University, Des Peres, Missouri
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Heckman found that virtually every woman had some degree of musculoskeletal discomfort during pregnancy; as many as one in four had at least temporarily disabling symptoms of some type.1 It is important to understand these conditions so that we can more effectively treat a woman who is pregnant.One of the physiologic changes that occurs during pregnancy is soft tissue swelling. Eighty percent of pregnant women report swelling during some stage of their pregnancy. Most had this during the last 8 weeks of pregnancy. This increased fluid can cause compression and lead to conditions such as carpal tunnel syndrome.Another change that occurs during pregnancy is increased ligamentous laxity, thought to be due to the hormones estrogen and relaxin. This laxity may lead to new injuries or increase the risk of injuries in individuals who already are ligamentously lax. This increased laxity, along with the normal weight gain that occurs during pregnancy, may cause increased discomfort in joints that have had previous injury or instability. A 20% weight gain during pregnancy may increase the force on a joint by as much as 100%.The changes occurring during pregnancy significantly affect the musculoskeletal system and may lead to new injuries or lower the threshold for many common conditions. This chapter will review many common orthopedic conditions that can occur during pregnancy, as well as discuss the effect of pregnancy or exercise.Low Back PainThis is one of the most common complications of pregnancy, occurring in as many as half of all pregnant women. It almost has been accepted as an inevitable part of pregnancy.2 Women who have had back pain before pregnancy are affected twice as often as those who have not had previous back pain. Previous pregnancy can also make the patient more susceptible to low back pain. Higher maternal age during pregnancy is also a risk factor for low back pain. Interestingly, no relationship has been found between low back pain in pregnancy and the height, weight, or weight gain of the mother.2The gravid uterus places an enormous mechanical strain on the lower back. The pelvis tends to rotate about a fulcrum at about the second sacral segment. The sacroiliac ligament resists forward rotation, and during pregnancy the tendency for rotation is increased as lumbar lordosis increases. This station shifts the center of gravity anteriorly, causing a strain on the low back and sacroiliac joint. As the strong sacroiliac ligaments become increasingly lax during the pregnancy, this allows an increase in the forward shift of the uterus, thereby placing even more strain on the pelvis and low back. A study that measured the levels of relaxin during pregnancy found that women who had been most incapacitated by low back pain had the highest amount of this hormone.3 The distention of the pelvis that occurs during pregnancy adds to this strain on the normal ligaments and causes a significant biomechanical change (Fig. 1). A spectrum of clinical symptoms may be produced by these changes.Unlike the above anatomic changes as a predisposing factor for low back pain, true herniation of a lumbar disk is rare. LaBan et al in 1983 documented the incidence of herniated disk to be around 1 in 10,000 pregnancies.4 An excellent study by Weinreb et al5 has shown that there is no difference in disk protrusion on MRI studies in women of childbearing age and those women who distinguished from a condition know as meralgia paresthetica.