What is the cause of red-orange colored urine in a pregnant female?

Red-Orange Colored Urine in Pregnancy

The most common causes of red-orange urine in pregnancy are urinary tract infection (the leading pathologic cause), concentrated urine from dehydration, and contamination from gynecologic bleeding—all of which require immediate urinalysis with microscopy to distinguish true hematuria from other etiologies. 1

Immediate Diagnostic Approach

First-Line Testing

• Obtain urinalysis with microscopy immediately to determine whether the discoloration represents true hematuria, hemoglobinuria, myoglobinuria, or simply concentrated urine 2
• Send urine culture regardless of symptoms, as asymptomatic bacteriuria affects 2-7% of pregnant women and requires treatment to prevent progression to pyelonephritis 2, 3
• Perform physical examination to distinguish urinary sources from gynecologic bleeding (cervical or vaginal), which can contaminate urine samples and mimic hematuria 1

Critical Initial Assessment

• Measure blood pressure immediately to rule out hypertensive disorders, defined as systolic BP ≥140 and/or diastolic BP ≥90 mm Hg 2
• Screen for proteinuria with automated dipstick; if ≥1+ (30 mg/dL), obtain spot urine protein/creatinine ratio, as preeclampsia can present with hematuria even in early pregnancy 2
• If hematuria occurs with hypertension or proteinuria, screen for preeclampsia immediately, as this represents a potential hypertensive emergency requiring hospitalization 1

Most Likely Etiologies in Order of Frequency

Urinary Tract Infection (Most Common Pathologic Cause)

• UTI is the leading pathologic cause of hematuria in pregnancy and should be excluded first with urinalysis and urine culture 1
• UTIs affect 5-7% of pregnant women and carry risk of complications for both mother and fetus due to high risk of ascending infection 3
• Approximately 30% of pregnant women with asymptomatic bacteriuria will develop pyelonephritis if not properly treated 4

Concentrated Urine from Dehydration

• Concentrated urine can appear red-orange without representing true hematuria, which is why microscopic examination is essential 2
• This is a benign finding that resolves with adequate hydration

Gynecologic Bleeding Contamination

• Subchorionic hematoma occurs in 7-27% of pregnancies and can present with vaginal bleeding that contaminates urine samples 1
• Cervical or vaginal bleeding must be distinguished from true hematuria through careful examination 1

Physiologic Hydronephrosis (After 20 Weeks)

• Physiologic hydronephrosis occurs in >80% of pregnant patients in the second and third trimester due to uterine compression on the ureter 5
• This alone is not a reliable sign of pathology but can be associated with microscopic hematuria 5

Imaging Strategy

First-Line Imaging

• Ultrasound of kidneys and bladder is the only appropriate first-line imaging because it avoids fetal radiation exposure and can identify most structural abnormalities 1, 2
• US is safe, rapid, portable, and does not require contrast material 5

Imaging to Avoid

• Avoid CT abdomen/pelvis and CT urography due to fetal radiation exposure 1, 2
• Avoid MRI with gadolinium contrast due to uncertain fetal effects 1, 2
• MRU without IV contrast is reasonable only after gynecologic bleeding and infection have been excluded, with full workup deferred until postpartum 5

Management Based on Findings

If UTI is Confirmed

• Treat with pregnancy-safe antibiotics immediately, as untreated bacteriuria increases risk of pyelonephritis from 20-35% to 1-4% with treatment 6
• Oral antibiotics for uncomplicated UTI include nitrofurans, fosfomycin trometamol, and third-generation cephalosporins (cefixime preferred due to high E. coli sensitivity) 3
• For pyelonephritis, hospitalize with IV beta-lactam antibiotics (cephalosporins or amoxicillin-clavulanate) until afebrile for 48 hours, then complete 4-7 days total treatment 6
• Fluoroquinolones are contraindicated in pregnancy despite being first-line in non-pregnant patients 6

If Subchorionic Hematoma is Suspected

• Obtain quantitative beta-hCG, complete blood count, and blood type/screen 1
• Transvaginal ultrasound is the primary diagnostic modality 1
• Administer anti-D immunoglobulin (50 μg) to Rh-negative patients with vaginal bleeding to prevent alloimmunization, even if source is uncertain 1

If No Benign Cause is Found

• Arrange postpartum follow-up at 3 months for comprehensive urologic evaluation if patient is asymptomatic 1
• The risk of malignancy in pregnant women with hematuria is low, and aggressive workup with radiation-based imaging is not justified 1, 5

Common Pitfalls to Avoid

• Do not dismiss dark urine as "normal pregnancy changes" without proper urinalysis, as this could miss significant pathology 2
• Do not withhold antibiotic treatment for confirmed bacteriuria, even if asymptomatic, as the risks of untreated infection far outweigh antibiotic risks in pregnancy 2
• Do not assume hydronephrosis alone indicates pathology after 20 weeks, as it is physiologic in >80% of cases 5
• Do not use fluoroscopy or CT imaging as first-line studies due to fetal radiation exposure 5