Differential Diagnosis for Back Pain in Pregnancy
Primary Diagnostic Categories
Back pain in pregnancy should be systematically categorized into three main groups: non-specific musculoskeletal pain (85% of cases), radiculopathy/spinal stenosis, or specific spinal pathology requiring urgent evaluation. 1
Non-Specific Musculoskeletal Pain (85% of Cases)
This represents the vast majority of pregnancy-related back pain and includes two distinct entities:
Lumbar Back Pain
- Mechanism: Pregnancy hormones cause ligamentous laxity that reduces ligament rigidity throughout the body, weakening joint stability and increasing demand on stabilizing muscles. 2, 3
- Biomechanical factors: The growing uterus shifts the center of gravity forward, creating additional load on the musculoskeletal system and forcing postural compensations that stress the spine. 2
- Prevalence: Affects up to two-thirds of pregnancies, with peak prevalence at 6-7 months gestation. 2, 1
- Clinical presentation: Pain is most pronounced with flexion and standing, consistent with discogenic or facet element pain. 4
Pelvic Girdle Pain (PGP)
- Prevalence: Occurs in approximately 20% of pregnancies and causes greater disability than lumbar pain. 2, 5
- Anatomical sites: Involves the symphysis pubis and/or sacroiliac joints, which experience softening and increased mobility from hormonal effects. 3, 6
- Clinical distinction: Can be differentiated from lumbar pain by pain location (anterior/posterior pelvic ring), intensity patterns, and positive pain provocation tests. 5
- Specific tests: Posterior pelvic provocation test, ventral/dorsal gapping tests, sacroiliac joint fixation test, Patrick's test (FABERE maneuver), and Derbolowski's test. 4
Radiculopathy or Spinal Stenosis
- Clinical signs: Sciatica, pseudoclaudication, motor deficits at multiple levels. 1
- Neurologic findings: Look for specific dermatomal sensory changes, reflex asymmetry, and focal motor weakness. 1
- Incidence: Neurologically symptomatic herniated discs are rare during pregnancy but can occur. 7
Specific Spinal Causes Requiring Urgent Evaluation
Cauda Equina Syndrome
- Red flags: Urinary retention, saddle anesthesia, bilateral leg weakness. 2
- Management: Represents a surgical emergency even during pregnancy and requires urgent MRI evaluation without gadolinium. 2, 1
Insufficiency/Stress Fractures
- Sacral fractures: Rare but documented in pregnancy, labor, or immediately postpartum, presenting with intractable lower back or pelvic pain and loss of mobility. 8
- Risk factors: Pregnancy-related osteoporosis (rare), vaginal delivery of high-birth-weight infant, increased lumbar lordosis, excessive weight gain, rapid vaginal delivery. 8
- Clinical presentation: Pain exacerbation with weight bearing, insidious onset. 8
- Imaging findings: Similar to sacral insufficiency fractures from osteoporosis, but occurring in reproductive-age women in third trimester or postpartum. 8
Femoral Neck Stress Fractures
- Types: Lateral tension-type (inherently unstable, high-risk, often requiring percutaneous screw fixation) versus medial compression-type (low-risk, treated with non-weight-bearing). 8
- Femoral head fractures: High-risk with increased rates of delayed union, nonunion, displacement, and avascular necrosis if not recognized promptly. 8
Infection or Malignancy
- Red flags: Fever, unexplained weight loss, history of cancer (increases post-test probability of cancer from 0.7% to 9%). 1
- Differential considerations: Sacroiliitis from inflammatory or infectious causes, osteitis condensans ilii. 8
Non-Spinal Causes (Referred Pain)
Intra-Abdominal Pathology
- Appendicitis: Most common non-obstetric surgical condition in pregnant women, occurring in 1 in 20 women of childbearing age. 1
- Other considerations: Pancreatitis, nephrolithiasis, ureteral stones, aortic aneurysm. 1
- Imaging approach: Ultrasound is the primary modality; MRI without contrast is second-line to avoid radiation exposure. 1
Obstetric Complications
- Warning signs: Regular and painful uterine contractions, vaginal bleeding, persistent loss of fluid from vagina, severe chest pain, persistent excessive shortness of breath, persistent dizziness or faintness. 2
Risk Factors to Identify
- Heavy lifting: Lifting 10-20 kg more than 20 times per week significantly increases musculoskeletal pain risk. 2, 3
- Obesity: Chronic overloading of connective tissue structures from elevated BMI. 2, 3
- Prior back pain: History of back pain before pregnancy predicts higher risk. 3, 4
- Multiparity: Multiple pregnancies increase risk. 4
Psychosocial Factors
- Impact of severe pain: Sleep disturbances, impaired activities of daily living, elevated depression risk, delayed resumption of postpartum physical activity. 2, 1
- Predictive value: Psychosocial factors predict risk of chronic disabling back pain and should be actively evaluated. 1
Critical Pitfalls to Avoid
- Underreporting: Women often fail to report back pain to prenatal providers, requiring active questioning by clinicians. 2, 1
- Inadequate screening: Missing red flags for cauda equina syndrome, infection, malignancy, or fracture can result in serious long-term morbidity. 2, 1
- Inappropriate imaging: Routine imaging without red flags wastes resources and provides no benefit; MRI without gadolinium is the safest modality when imaging is necessary. 1
- Overlooking non-spinal causes: Failing to consider appendicitis or other intra-abdominal pathology in the differential. 1