Differential Diagnosis for Back Pain in Pregnancy
Primary Diagnostic Framework
Back pain in pregnancy must be systematically categorized into three distinct 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 is the most common category and includes two distinct subtypes that should be differentiated:
Lumbar Back Pain
- Pain localized over and around the lumbar spine, exacerbated by flexion and prolonged standing 2, 3
- Caused by pregnancy hormones (particularly relaxin, which increases ten-fold) creating ligamentous laxity that weakens joint stability and increases demand on stabilizing muscles 1, 2
- The growing uterus shifts the center of gravity forward, forcing postural compensations that stress the spine 1
- Affects up to two-thirds of pregnancies, with peak prevalence at 6-7 months gestation 1, 4
Pelvic Girdle Pain
- Pain between the posterior iliac crest and gluteal fold, involving anterior and/or posterior aspects of the pelvic ring 4, 3
- Affects nearly 20% of pregnant women and results in greater disability than lumbar pain 5, 6
- Most prominent in the symphysis pubis and sacroiliac joints due to hormone-induced joint laxity 2
- Can be distinguished from lumbar pain through pain provocation tests including posterior pelvic provocation test, ventral/dorsal gapping tests, and Patrick's test 2
Risk Factors to Identify
- Prior back pain before pregnancy is the strongest predictor 2, 7
- Heavy lifting (10-20 kg more than 20 times per week) 1, 4
- Obesity and multiparity 1, 2
- Back pain during menstruation 7
Radiculopathy or Spinal Stenosis
Clinical Presentation
- Sciatica: pain radiating down the leg below the knee in sciatic nerve distribution 8
- Pseudoclaudication: leg pain on walking/standing, relieved by sitting or spinal flexion 8, 9
- Neurologic findings: dermatomal sensory changes, reflex asymmetry, focal motor weakness at multiple levels 1, 9
Lumbar Disc Herniation
- Most common spinal disorder during pregnancy that can cause permanent neurologic deficit 7
- Presents with radicular symptoms and positive straight-leg-raise test (reproduction of sciatica when leg raised between 30-70 degrees) 8
Specific Spinal Causes Requiring Urgent Evaluation
Cauda Equina Syndrome
- Surgical emergency even during pregnancy requiring urgent MRI without gadolinium 1, 9
- Red flag symptoms: urinary retention or incontinence, bilateral motor weakness of lower extremities, saddle anesthesia 8, 4
- Caused by massive central disc herniation compressing lower cord nerve roots 8
Sacral Fractures
- Rare but documented in pregnancy, labor, or immediately postpartum 1
- Presents with intractable lower back or pelvic pain and loss of mobility 1
Pregnancy-Related Osteoporotic Fractures
- Transient osteoporosis and vertebral compression fractures can occur during pregnancy 5, 7
- More common in third trimester and postpartum period 7
Spinal Tumors
- Vertebral hemangiomas may become symptomatic during pregnancy due to hormonal changes 7
- Red flags include unexplained weight loss, history of cancer, or fever (increases post-test probability of cancer from 0.7% to 9%) 9
Infection
- Fever combined with back pain warrants urgent evaluation for spinal infection 9
- Progressive neurological deficits suggest epidural abscess or discitis 9
Non-Spinal Causes (Referred Pain)
Intra-Abdominal Pathology
- Appendicitis: most common non-obstetric surgical condition in pregnant women (1 in 20 women of childbearing age) 1, 9
- Nephrolithiasis/ureteral stones: can present as flank or back pain 1, 9
- Pancreatitis: epigastric pain radiating to back 1, 9
- Aortic aneurysm: rare but life-threatening cause of back pain 1, 9
Obstetric Causes
- Placental abruption: severe back pain with vaginal bleeding and uterine contractions 8
- Labor: regular, painful uterine contractions with back pain 8
- Ectopic pregnancy (first trimester): unilateral pelvic/back pain with positive β-hCG 8
Other Musculoskeletal Conditions
- Pubic symphysis rupture: severe anterior pelvic pain with inability to bear weight 5
- Femoral neck stress fractures: groin/hip pain that may radiate to back 1
- Carpal tunnel syndrome: though not causing back pain, commonly co-occurs 5
Psychosocial Factors
Severe pain significantly impacts sleep, daily activities, and mental health, and psychosocial factors predict risk of chronic disabling back pain 1, 9. Women with higher pain severity during pregnancy are at higher risk for persistent postpartum pain 4.
Critical Pitfalls to Avoid
- Underreporting by patients: requires active questioning by healthcare providers, as women often fail to report back pain to prenatal providers 1, 9
- Missing red flags: failure to screen for cauda equina symptoms, progressive neurologic deficits, fever, or cancer history can result in serious long-term morbidity 1, 9
- Inappropriate imaging: routine imaging without red flags wastes resources and provides no benefit; MRI without gadolinium is safest when imaging is necessary 9
- Overlooking non-spinal causes: failing to consider appendicitis, nephrolithiasis, or other intra-abdominal pathology can delay critical diagnosis 1, 9
- Neglecting psychosocial evaluation: psychosocial factors contribute significantly to pain perception and disability 9