Is Amoxicillin safe during pregnancy?

Pregnancy category and evidence

Amoxicillin is a penicillin-class antibiotic with decades of pregnancy safety data. Under the former FDA category system it was Category B — animal studies showed no fetal risk and human data have not demonstrated teratogenicity. Large cohort studies (hundreds of thousands of exposures) have not found increased rates of major malformations. ACOG and RCOG classify it as an acceptable first-line choice for common infections during pregnancy.

By trimester

• First trimester (weeks 1–12): amoxicillin is among the most-studied antibiotics in early pregnancy; registry data show no significant increase in birth defects. It remains first-line for uncomplicated UTIs, dental infections, and susceptible respiratory infections.
• Second trimester (13–27): considered safe; routine use for listeriosis, pyelonephritis, and GBS chemoprophylaxis continues.
• Third trimester (28–40): safe; commonly used in intrapartum prophylaxis for Group B Streptococcus (GBS)-positive mothers (2 g IV load, then 1 g every 4 hours until delivery).

Safer alternatives

Amoxicillin itself is considered one of the safer antibiotic options in pregnancy. If a patient has a penicillin allergy, alternatives include:

• Cephalexin (if non-anaphylactic reaction history; cross-reactivity ~1–2%)
• Azithromycin (for respiratory infections; Category B)
• Nitrofurantoin (for UTIs; avoid at term due to neonatal hemolysis risk)

Avoid tetracyclines (teeth/bone effects) and fluoroquinolones (cartilage concerns) throughout pregnancy.

When it's acceptable and when to be cautious

Amoxicillin is acceptable in all trimesters for evidence-based indications. Cautions:

• Clostridioides difficile risk: as with any antibiotic, diarrhea monitoring.
• Penicillin allergy: document the reaction type; severe reactions (anaphylaxis) contraindicate penicillins.
• Rare immune hemolytic anemia: if baseline anemia is concerning, monitor.

Clinical sources

• FDA Pregnancy Labeling Rule (PLLR) 2015 — applied narrative labeling replacing letter categories; amoxicillin labels describe no observed risk.
• ACOG Committee Opinion 717 "Sulfonamides, Nitrofurantoin, and Risk of Birth Defects" (for context on antibiotic comparisons).
• RCOG Green-top Guideline 36 "The Prevention of Early-onset Neonatal Group B Streptococcal Disease."
• Muanda FT et al. "Use of antibiotics during pregnancy and risk of spontaneous abortion." CMAJ 2017 (PMID: 28461374).

Bottom line

Amoxicillin is one of the best-studied and safest antibiotics in pregnancy across all three trimesters. It is routinely used for UTIs, respiratory infections, dental infections, and GBS prophylaxis. Document any penicillin allergy with your obstetrician.

Never start, stop, or change pregnancy medications without consulting your obstetrician or healthcare provider.