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Safer antibiotics in pregnancy

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antibiotics pregnancy safety ACOG antimicrobial use pregnancy penicillin cephalosporin nitrofurantoin

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Commonly considered safer antibiotics in pregnancy, when there is a clear bacterial indication and the drug is chosen for the infection and culture result:
  • Penicillins: amoxicillin, ampicillin, penicillin V, amoxicillin-clavulanate
  • Cephalosporins: cephalexin, cefuroxime, ceftriaxone
  • Macrolides: azithromycin and erythromycin (some formulations are preferred over others)
  • Clindamycin
  • Metronidazole: generally used when indicated, including for certain vaginal, dental, or abdominal infections
  • Nitrofurantoin: commonly used for lower urinary tract infection. Avoid for suspected kidney infection because it does not reach adequate kidney tissue levels; it may also be avoided near delivery in certain situations, such as known G6PD deficiency.
  • Fosfomycin: an option for uncomplicated lower UTI.
Antibiotics that are usually avoided or used only for specific reasons in pregnancy:
  • Tetracyclines such as doxycycline: can affect fetal teeth and bone, especially after early pregnancy.
  • Fluoroquinolones such as ciprofloxacin: alternatives are generally preferred.
  • Trimethoprim-sulfamethoxazole (co-trimoxazole): may be avoided in the first trimester because trimethoprim interferes with folate metabolism, and near term because of newborn risks. It can still be used when benefits outweigh risks, often with folate advice.
  • Aminoglycosides such as gentamicin: reserved for serious infections because of potential fetal toxicity, with specialist oversight.
Do not take leftover antibiotics or choose an antibiotic solely based on pregnancy safety. The right medicine depends on the infection site, gestational age, allergy history, local resistance, and culture results. Seek urgent assessment for fever, flank/back pain, vomiting, shortness of breath, severe abdominal pain, or reduced fetal movement.
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pregnancy AND antibiotics

No antibiotic is universally “safe” for every infection or trimester. The safest choice depends on the infection, culture result, allergy history, gestational age, and maternal condition. Untreated serious infection can also harm pregnancy.
Commonly preferred options when clinically indicated
  • Penicillins: penicillin V, amoxicillin, ampicillin, flucloxacillin/dicloxacillin
  • Cephalosporins: cefalexin/cephalexin, cefuroxime, ceftriaxone
  • Clindamycin: often used when a beta-lactam cannot be used, depending on infection and susceptibility
  • Metronidazole: generally used when needed for specific anaerobic, dental, vaginal, or gastrointestinal infections
  • Azithromycin or erythromycin: may be used for particular infections such as chlamydia, but are not blanket substitutes for penicillin
  • Fosfomycin and nitrofurantoin: commonly used for uncomplicated lower UTI, not for kidney infection. ACOG lists nitrofurantoin, beta-lactams, sulfonamides, and fosfomycin among options for pregnancy-associated cystitis, with culture-guided selection preferred. ACOG UTI guidance
Use with particular caution or usually avoid
  • Tetracyclines such as doxycycline: generally avoided after early pregnancy because of fetal tooth and bone effects.
  • Fluoroquinolones such as ciprofloxacin or levofloxacin: usually avoided when suitable alternatives exist.
  • Trimethoprim-sulfamethoxazole (co-trimoxazole): often avoided in the first trimester if alternatives exist because trimethoprim affects folate metabolism; also generally avoided near delivery because of neonatal bilirubin concerns. It can still be prescribed if benefits outweigh risks and alternatives are unsuitable.
  • Nitrofurantoin: avoid in people with G6PD deficiency and clinicians may avoid it near delivery; it does not treat pyelonephritis because it does not reach adequate kidney tissue levels.
  • Aminoglycosides such as gentamicin: reserved for significant infections under specialist supervision.
Important practical points
  1. Do not self-start leftover antibiotics or take an antibiotic prescribed for someone else.
  2. Ask for a urine culture for suspected UTI in pregnancy when possible, then tailor treatment to susceptibility.
  3. Tell the prescriber your exact pregnancy week, drug allergies, G6PD status if known, and any prior resistant infections.
  4. Fever, flank/back pain, vomiting, feeling very unwell, or contractions with urinary symptoms needs urgent assessment, as kidney infection in pregnancy may require hospital IV antibiotics.
Recent systematic reviews continue to assess potential associations from prenatal antibiotic exposure, but observational associations do not mean a needed antibiotic should be withheld. Prescribe the narrowest effective agent for the shortest appropriate course.
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