What is the recommended treatment regimen for a pregnant woman with tuberculosis (TB)?

Treatment of Tuberculosis in Pregnancy

Pregnant women with active tuberculosis should be treated immediately with a three-drug regimen of isoniazid, rifampin, and ethambutol, as untreated TB poses far greater risks to both mother and fetus than the medications themselves. 1, 2

Initial Treatment Regimen

The standard first-line treatment consists of:

• Isoniazid (INH) - 10 mg/kg daily, maximum 600 mg/day 3
• Rifampin (RIF) - 10 mg/kg daily, maximum 600 mg/day 3
• Ethambutol (EMB) - standard dosing 1, 2
• Pyridoxine (Vitamin B6) - 25 mg/day supplementation is mandatory for all pregnant women receiving isoniazid to prevent neurotoxicity 1, 2

These three drugs (INH, RIF, EMB) have extensive safety data in pregnancy and are not associated with human fetal malformations. 4, 5

Critical Medications to Avoid

Streptomycin and all aminoglycosides (kanamycin, amikacin, capreomycin) are absolutely contraindicated in pregnancy - they cause eighth nerve damage and congenital deafness in approximately 17% of exposed fetuses. 1, 2 This is the only anti-TB drug with documented harmful effects on the human fetus. 1

Pyrazinamide (PZA) is generally not recommended in the United States during pregnancy due to insufficient teratogenicity data, though WHO and international organizations do recommend its routine use. 1, 2 Some U.S. public health jurisdictions have used it without reported adverse events, and it may be considered after the first trimester in HIV-infected women. 1

Fluoroquinolones should be avoided due to their association with arthropathies in young animals. 1, 2

Treatment Duration

If pyrazinamide is NOT included in the regimen, the minimum treatment duration is 9 months (typically 2 months of INH/RIF/EMB followed by 7 months of INH/RIF). 1, 2

If pyrazinamide IS used (following international guidelines or in specific high-risk situations), the standard 6-month regimen applies: 2 months of four-drug therapy followed by 4 months of INH/RIF. 1

Monitoring Requirements

Close clinical and laboratory monitoring is essential because:

• Pregnant women and those in the early postpartum period (within 3 months of delivery) may have increased vulnerability to isoniazid hepatotoxicity 1
• Baseline liver function tests (AST/ALT and bilirubin) should be obtained before starting treatment 1
• Monthly clinical evaluations are required, including questioning about hepatitis symptoms (nausea, vomiting, abdominal pain, jaundice, dark urine) 1
• More frequent monitoring (at 2,4, and 6 weeks) may be warranted given pregnancy-related hepatotoxicity risk 1

Patients should be educated to stop treatment immediately and seek medical evaluation if signs of hepatitis develop. 1

Special Considerations for Timing

Treatment should be initiated without delay regardless of trimester - the risk of untreated TB far outweighs any theoretical medication risks. 1, 2 Infants born to women with untreated TB may have lower birth weight and, rarely, acquire congenital tuberculosis. 1

For latent TB infection (not active disease) in pregnant women:

• High-risk patients (HIV-infected or recent infection) should receive treatment during pregnancy, even in the first trimester 1
• Lower-risk patients may have treatment deferred until after delivery, though this remains controversial 1

Breastfeeding

Breastfeeding should NOT be discouraged for women on first-line anti-TB drugs, as the small concentrations in breast milk (less than 20% of therapeutic infant levels) do not produce toxic effects. 1, 2 However, these amounts are inadequate for treating or preventing TB in the infant. 1

Infants breastfeeding from mothers on isoniazid should receive supplemental pyridoxine. 1

Drug-Resistant Tuberculosis

For multidrug-resistant TB in pregnancy, expert consultation is mandatory. 2 Counseling about risks to the fetus should be provided due to the known and unknown risks of second-line agents. 1 However, termination of pregnancy is not medically indicated for women taking first-line anti-TB drugs. 1, 5

Common Pitfalls to Avoid

• Never substitute streptomycin for ethambutol - this is explicitly contraindicated due to ototoxicity 1
• Do not delay treatment waiting for the second trimester - active TB requires immediate treatment 1, 2
• Do not forget pyridoxine supplementation - this is mandatory, not optional 1, 2
• Do not assume drugs in breast milk provide adequate infant prophylaxis - they do not 1
• Do not use rifampin-pyrazinamide regimens for latent TB in pregnancy due to hepatotoxicity concerns 1