Cotrimoxazole Use in Pregnancy

General Considerations

• Cotrimoxazole can be used with more confidence during the second and third trimesters when the risk of neural tube defects is lower, according to the European Respiratory Society guidelines 1
• For pregnant women prescribed cotrimoxazole in the third trimester, clinicians should be aware of the risk for neonatal hyperbilirubinemia, as recommended by the CDC 2, 3

Specific Clinical Scenarios

• In Q fever infections during pregnancy, long-term cotrimoxazole therapy is recommended to decrease the risk of placentitis, obstetric complications, and maternal chronic Q fever infection, as suggested by the British Journal of Pharmacology 4, 5, 6

Risk Mitigation Strategies

• All women capable of becoming pregnant should consume at least 400 μg of folic acid daily from supplements, fortified foods, or both, to reduce the risk of neural tube defects, especially if taking cotrimoxazole, as recommended by the CDC 2, 3
• The CDC has assessed the risks and benefits of cotrimoxazole in certain infectious diseases and determined that the risk of acquiring serious infections like Q fever outweighs the risk of antimicrobial drug-related adverse effects, with guidance from the British Journal of Pharmacology 4, 5

Alternative Antibiotics During Pregnancy

• For patients with penicillin allergy, macrolides (except erythromycin estolate) may be considered as alternatives, according to the European Respiratory Society guidelines 1

Bactrim Use in Pregnancy

Risk Profile by Trimester

• The American Academy of Dermatology recommends avoiding Bactrim during pregnancy, particularly in the first trimester and near term, due to risks of congenital malformations and neonatal complications, though it may be used in the second trimester when safer alternatives are unavailable and the maternal infection poses greater risk than the medication 7, 8
• The 2025 hidradenitis suppurativa guidelines specifically recommend avoiding oral co-trimoxazole in pregnant patients due to increased risk of preterm birth, low birthweight, and kernicterus 7

Risk Mitigation Strategies

• The American Academy of Dermatology suggests using oral cephalexin, azithromycin, or clindamycin as safer systemic antibiotic options during pregnancy 7

Clinical Decision Algorithm

• The European Respiratory Society guidelines classify co-trimoxazole as "avoid" during pregnancy but note it is "possibly safe" during breastfeeding, and absolute contraindications include first trimester exposure and near term or at delivery 8
• The American Academy of Dermatology recommends considering Bactrim in the second trimester when safer alternatives have failed or are contraindicated 7

Breastfeeding Considerations

• The European Respiratory Society guidelines note that co-trimoxazole is compatible with breastfeeding in healthy term babies, but caution should be exercised when administering to nursing women with jaundiced, ill, stressed, or premature infants 8

Cotrimoxazole Use in Pregnancy

Specific Clinical Scenarios

• Long-term cotrimoxazole therapy (320 mg trimethoprim and 1600 mg sulfamethoxazole for 35 days) is specifically recommended for pregnant women with Q fever to decrease the risk of placentitis, obstetric complications, and maternal chronic Q fever infection, as the benefits clearly outweigh the risks, with Q fever potentially causing intrauterine fetal death related to placental infection 9

Trimethoprim Use Around Conception: Significant Risks Requiring Caution

Risk Profile and Mitigation Strategies

• The FDA classifies trimethoprim as Pregnancy Category C, stating it may interfere with folic acid metabolism and should only be used if potential benefits justify risks to the fetus, according to the American Academy of Dermatology 10
• Trimethoprim-sulfamethoxazole may increase risk of congenital abnormalities including urinary tract and cardiovascular abnormalities due to antifolate effects, as reported by the Centers for Disease Control and Prevention 11, 12, 13
• All women of childbearing potential taking trimethoprim should consume at least 400 μg of folic acid daily from supplements or fortified foods to reduce the risk of neural tube defects, as recommended by the Centers for Disease Control and Prevention 11, 12
• When trimethoprim is being considered around conception or during pregnancy, it should be avoided if possible, especially during the 12 weeks before planned conception and throughout the first trimester, according to the American Academy of Dermatology 10
• If trimethoprim must be used, high-dose folic acid supplementation (at least 400 μg daily) should be prescribed, and the patient should be monitored for adverse pregnancy outcomes, as recommended by the Centers for Disease Control and Prevention 11, 12
• Clinicians should be aware of the risk for neonatal hyperbilirubinemia and kernicterus when cotrimoxazole is prescribed in the third trimester, according to the American Academy of Dermatology 10

Bactrim for MRSA in Pregnancy

General Guidelines

• The Infectious Diseases Society of America guidelines classify TMP-SMX as pregnancy category C/D and specifically recommend against use in the third trimester 14, 15, 16
• The American Academy of Dermatology suggests considering Bactrim in the second trimester only when safer alternatives have failed or are contraindicated, although this specific recommendation is not directly cited, a similar guideline from the same society is available for another condition 17
• Vancomycin remains the preferred agent for serious invasive MRSA infections requiring hospitalization 14, 15, 16

Treatment Options

• Cephalexin is considered safe throughout pregnancy with no adverse effects reported in non-HS studies 17
• Azithromycin is safe in pregnancy with no adverse effects reported 17
• Clindamycin has moderate evidence supporting safety in pregnancy, though it is bacteriostatic with potential for cross-resistance in erythromycin-resistant strains 14, 15, 16, 17
• Vancomycin is the mainstay of parenteral therapy for MRSA infections and the drug of choice for penicillin-allergic patients 14, 15, 16

Clinical Decision Algorithm

• For skin and soft tissue infections (SSTI): Incision and drainage is the primary treatment; antibiotics are indicated for severe/extensive disease, rapid progression with cellulitis, systemic illness, comorbidities, or failure of drainage alone 14, 15
• For invasive infections (bacteremia, endocarditis, pneumonia): Parenteral vancomycin is preferred 14, 15, 16
• 95-100% of community-acquired MRSA strains are susceptible to TMP-SMX in vitro 14, 15, 16

Special Considerations

• TMP-SMX is not FDA-approved for treatment of any staphylococcal infections, though it has become an important option for outpatient SSTI due to high in vitro susceptibility 14, 15, 16
• Clinical experience with TMP-SMX for invasive MRSA infections is limited, particularly in pregnant populations 14, 15, 16
• For outpatient SSTI, 5-10 days of therapy is recommended based on clinical response 14, 15
• Longer courses may be needed for bone/joint infections or invasive disease 14, 15