First-Line Antibiotics During Pregnancy
The first-line antibiotics recommended for use during pregnancy are penicillins (particularly amoxicillin) and cephalosporins (such as cephalexin), as they have established safety profiles and are considered appropriate for most common infections during pregnancy. 1
Safe First-Line Antibiotics in Pregnancy
Penicillins: Penicillin G and amoxicillin are preferred due to their narrow spectrum of activity and established safety profile. Amoxicillin is classified as safe during pregnancy with no evidence of harm to the fetus in animal or human studies. 2
Cephalosporins: Cephalexin and other cephalosporins are considered safe alternatives, particularly for penicillin-allergic patients without history of anaphylaxis. 1
Azithromycin: Safe for use in pregnancy with no adverse effects reported in studies of pregnant patients. 1
Clindamycin: Moderate evidence supports its safety in pregnancy, though it should be used with awareness of potential gastrointestinal effects in infants if used while breastfeeding. 1
Infection-Specific Recommendations
Urinary Tract Infections
- First-line: Amoxicillin, cephalexin 3, 4
- Second-line: Amoxicillin-clavulanate, cefuroxime 3
- Note: While nitrofurantoin is commonly prescribed for UTIs, it should be avoided after 37 weeks of pregnancy due to risk of neonatal hemolytic anemia. 3, 4
Group B Streptococcal Infection
- First-line: Penicillin G (5 million units IV initial dose, then 2.5 million units IV every 4 hours until delivery) 1
- Alternative: Ampicillin (2 g IV initial dose, then 1 g IV every 4 hours until delivery) 1
- For penicillin allergy without anaphylaxis risk: Cefazolin (2 g IV initial dose, then 1 g IV every 8 hours) 1
- For penicillin allergy with anaphylaxis risk: Clindamycin or vancomycin (if susceptibility testing confirms sensitivity) 1
Sexually Transmitted Infections
- Chlamydia:
Antibiotics to Avoid During Pregnancy
Tetracyclines (including doxycycline): Contraindicated after the fifth week of pregnancy due to risk of dental staining and potential bone growth inhibition in the fetus. 1, 5
Fluoroquinolones (e.g., ciprofloxacin): Generally avoided during pregnancy due to potential risks to fetal cartilage development. 5, 6
Trimethoprim-sulfamethoxazole (TMP-SMX): Should be avoided, particularly in the first trimester due to potential risk of birth defects and near term due to risk of neonatal hyperbilirubinemia. 1, 4
Aminoglycosides: Should be avoided when possible due to potential risks of ototoxicity and nephrotoxicity in the fetus. 1, 5
Important Clinical Considerations
Screening and prophylaxis: All pregnant women should be screened for asymptomatic bacteriuria and Group B Streptococcus (at 35-37 weeks gestation). 1
Treatment duration: Varies by infection type - single dose to 7-14 days depending on the specific infection and severity. 3, 7
Physiological changes: Pregnancy causes increased glomerular filtration rate and total body volume, which may necessitate dosage adjustments for some antibiotics. 6
Antimicrobial stewardship: Avoid unnecessary antibiotic use during pregnancy. Prophylactic antibiotics should not be used before the intrapartum period to treat GBS colonization as this is ineffective and may cause adverse consequences. 1
Post-treatment follow-up: For certain infections like UTIs, a follow-up urine culture 1-2 weeks after treatment completion is recommended to confirm cure. 3, 7
Remember that the choice of antibiotic should be guided by the specific infection, local resistance patterns, and individual patient factors, but penicillins and cephalosporins remain the safest first-line options for most infections during pregnancy.