Which antibiotics are safe to use during pregnancy?

Antibiotics Safe in Pregnancy

Penicillins and cephalosporins are the safest first-line antibiotics during pregnancy and should be prioritized for most infections. 1

Safest Options (Compatible Throughout Pregnancy)

Beta-Lactams - First Choice

• Amoxicillin: Compatible throughout all trimesters and considered low risk 1
• Amoxicillin-clavulanic acid: Compatible, though avoid in women at risk of preterm delivery due to very low risk of necrotizing enterocolitis 1
• Ampicillin: Recommended for intrapartum GBS prophylaxis (2g IV initial dose, then 1g IV every 4 hours until delivery) 2, 3
• Penicillin G: Preferred agent for GBS prophylaxis due to narrow spectrum (5 million units IV initial dose, then 2.5-3.0 million units every 4 hours) 2, 3
• Cephalexin: Suggested for systemic infections in pregnancy with moderate evidence of safety 4
• Cefuroxime: Compatible throughout pregnancy with human data indicating no teratogenicity at therapeutic doses 1
• Ceftazidime: Compatible, with cephalosporins generally safe in pregnancy 1
• Cefazolin: Preferred for penicillin-allergic patients not at high risk for anaphylaxis (2g IV initial dose, then 1g IV every 8 hours) 2, 3
• Piperacillin-tazobactam: Compatible, with all penicillins considered low risk 1

Macrolides - Generally Safe

• Azithromycin: Probably safe with moderate evidence; very low risk of hypertrophic pyloric stenosis only in first 13 days of breastfeeding 1, 4
• Erythromycin: Probably safe in T2/T3, though avoid erythromycin estolate due to maternal hepatotoxicity 1

Other Safe Options

• Nitrofurantoin: Generally safe and effective, preferred 4-7 day course over single dose 5, 6
• Fosfomycin: Single dose effective for bacteriuria clearance, though limited pregnancy outcome data 5
• Clindamycin: Suggested for use with moderate evidence of safety; can be used with rifampin for severe hidradenitis suppurativa 4

Use With Caution (Possibly Safe in Specific Situations)

Second-Line Agents

• Metronidazole: Use only if no safer alternatives available; possibly safe but stop breastfeeding 12-24 hours after single 2g dose 1
• Vancomycin: Probably safe in T2/T3, compatible; limited T1 experience 1
• Meropenem: Possibly safe in T1, probably safe in T2/T3 1
• Ciprofloxacin: Possibly safe but most clinicians avoid; animal studies suggest cartilage damage risk though human data suggest low risk 1
• Rifampin: Possibly safe but give with vitamin K to prevent neonatal bleeding; first-line for tuberculosis only 1

Antibiotics to AVOID

Contraindicated or High Risk

• Doxycycline and tetracyclines: AVOID in T2/T3 - associated with tooth discoloration and bone growth suppression; may exacerbate maternal fatty liver 1, 4
• Aminoglycosides (gentamicin, tobramycin): AVOID if possible - eighth cranial nerve toxicity risk (streptomycin documented); use only for severe infections when other antibiotics fail 1
• Co-trimoxazole (trimethoprim-sulfamethoxazole): AVOID especially in T1 - associated with hyperbilirubinemia, fetal hemolytic anemia, preterm birth, low birthweight, and kernicterus 1, 4
• Trimethoprim: AVOID in T1 - use short courses only if necessary with folic acid supplementation 1
• Fluoroquinolones: Generally avoided due to theoretical arthropathy risk in children, though human data suggest lower risk than previously thought 7, 6
• Erythromycin: AVOID - may increase risk of adverse outcomes including elevated liver enzymes 4
• Dapsone: AVOID - increased risk of preterm birth, low birthweight, and hemolysis 4

Key Clinical Considerations

Penicillin Allergy Management

For patients with penicillin allergy history 2, 3:

• Low-risk (no anaphylaxis history): Use cefazolin as preferred alternative
• High-risk (anaphylaxis, angioedema, respiratory distress, urticaria):
  • If GBS isolate susceptible to clindamycin AND erythromycin: Use clindamycin 900mg IV every 8 hours
  • If resistance or unknown susceptibility: Use vancomycin 1g IV every 12 hours

Important Caveats

• Physiologic changes in pregnancy alter pharmacokinetics - increased glomerular filtration, expanded volume, enhanced cardiac output may require dose adjustments for renally cleared antibiotics 6, 8
• Duration matters: For asymptomatic bacteriuria in pregnancy, 4-7 day courses are more effective than single-dose therapy, particularly for nitrofurantoin and beta-lactams 5
• Breastfeeding: Beta-lactam antibiotics are generally safe during lactation; avoid tetracyclines and fluoroquinolones due to developmental concerns 9, 6