Which pregnancy safety category does amoxicillin belong to?

October 12, 2025 •

3 min read

Before 2015, the U.S. Food and Drug Administration (FDA) classified amoxicillin as Pregnancy Category B. This historical classification is important, but it's crucial for pregnant individuals to understand the modern Pregnancy and Lactation Labeling Rule (PLLR) that has since replaced the letter-based system.

Quick Summary

Amoxicillin was formerly a Pregnancy Category B drug, but the FDA replaced this system with the PLLR in 2015. Under the new guidelines, amoxicillin remains generally considered safe, with the overall benefits of treating maternal infections outweighing minimal risks during pregnancy and breastfeeding.

Key Points

Former Category B Designation: Under the old FDA system, amoxicillin was classified as Pregnancy Category B, indicating animal studies showed no harm to the fetus.
New PLLR Labeling: Since 2015, the FDA replaced the letter-based categories with the Pregnancy and Lactation Labeling Rule (PLLR), providing narrative summaries of drug risk and benefits.
Generally Considered Safe: A large body of clinical data supports the general safety of amoxicillin use during all stages of pregnancy when medically needed, with no consistent link to major birth defects.
Breastfeeding Safety: Amoxicillin is considered safe while breastfeeding, as only minimal amounts pass into breast milk. Mild side effects like rash or diarrhea in the infant are rare.
Consult a Doctor: It is crucial for pregnant and breastfeeding individuals to consult a healthcare provider before taking amoxicillin or any medication to discuss the specific risks and benefits.
Benefit vs. Risk: Treating a serious bacterial infection with amoxicillin is often safer than leaving the infection untreated, which can pose significant risks to both mother and baby.
Controversial Studies: While some older studies suggested a potential link to oral clefts, larger, more recent research has found no such association, making this a highly debated and unsubstantiated claim.

Understanding the Former FDA Pregnancy Categories

For decades, the U.S. Food and Drug Administration (FDA) used a five-letter system (A, B, C, D, and X) to classify the potential risks of medications used during pregnancy. This system, developed in 1979, aimed to help doctors assess drug safety.

Category A: Adequate human studies showed no risk in the first trimester or later.
Category B: Animal studies showed no risk, or animal studies showed risk but human studies did not.
Category C: Animal studies showed adverse effects, but human data was lacking. Potential benefits might outweigh risks.
Category D: Positive evidence of human fetal risk exists, but benefits might justify use in serious situations.
Category X: Animal or human studies show fetal abnormalities or risk that clearly outweighs any benefit. Contraindicated in pregnancy.

Under this old system, amoxicillin was classified as Pregnancy Category B.

The Shift to the Modern PLLR System

In 2015, the FDA replaced the letter categories with the Pregnancy and Lactation Labeling Rule (PLLR). This change addressed concerns that the old system was too simple and sometimes misunderstood.

The PLLR provides detailed narrative information in three sections: Pregnancy, Lactation, and Females and Males of Reproductive Potential.

Comparing the Old vs. New Labeling Systems


Feature	Old FDA Letter Categories	New FDA PLLR System
Classification Type	Single letter (A, B, C, D, X)	Narrative summaries and subsections
Information Conveyed	Limited, generalized risk assessment	Detailed, integrated discussion of risks, benefits, and data
Focus	Primarily fetal risk, based on available data	Comprehensive, addressing maternal, fetal, and breastfeeding risks
Flexibility	Rigid, no context for individual cases	Allows healthcare providers to make more informed, contextual decisions
Updating	Labels are not automatically updated	Requires manufacturers to update labels as new information becomes available

Amoxicillin Safety Under the Modern PLLR

Extensive data and clinical research since the old categorization support amoxicillin's safety during pregnancy when medically necessary. Untreated bacterial infections often pose greater risks to both mother and fetus than amoxicillin.

Studies have not consistently linked amoxicillin to major birth defects or adverse outcomes. For example, a large study with over 100,000 pregnancies found no increased risk of major birth defects with first-trimester amoxicillin exposure.

A Note on Conflicting Data Some older studies suggested a potential, though controversial, link between first-trimester amoxicillin and oral clefts. However, larger, well-controlled studies contradict these findings, and the medical consensus considers amoxicillin safe.

Amoxicillin and Breastfeeding

Amoxicillin is considered safe while breastfeeding according to health organizations and available data.

Low Excretion: Very small amounts of amoxicillin enter breast milk (around 1% relative infant dose).
Acceptable Use: The American Academy of Pediatrics deems amoxicillin acceptable during lactation.
Monitoring: While rare, monitor infants for mild side effects like diarrhea, rash, or oral thrush and consult a healthcare professional with concerns.

Making an Informed Decision

Decisions about using amoxicillin during pregnancy or breastfeeding require consultation with a healthcare provider. They will evaluate the benefits of treating the infection against potential minimal risks. Untreated infections can have serious consequences for both mother and baby. The PLLR provides clearer, data-driven information for this discussion.

Commonly Prescribed Safe Antibiotics During Pregnancy Other antibiotics generally considered safe in pregnancy include:

Penicillins: Penicillin V, ampicillin.
Cephalosporins: Cephalexin, cefaclor.
Macrolides: Erythromycin, azithromycin.
Other: Clindamycin.

Antibiotics to Generally Avoid During Pregnancy Some antibiotics are usually avoided due to potential risks:

Tetracyclines: Risk to developing bones and teeth.
Fluoroquinolones: Possible risk of musculoskeletal issues.
Sulfonamides: Linked to birth defects in early pregnancy.

Conclusion

Under the current system, asking which pregnancy safety category does amoxicillin belong to is no longer the key question. The extensive medical evidence confirms amoxicillin's safety for use during pregnancy when medically necessary. Formerly Category B, it remains a common and effective antibiotic for pregnant individuals. Consulting a healthcare provider is essential to assess individual circumstances and ensure the best outcome for both mother and baby, as untreated infections pose significant dangers.

Frequently Asked Questions

The old system used a simple A, B, C, D, or X letter to indicate risk, which was often misinterpreted. The new PLLR system provides a detailed narrative summary of risk, benefits, and data across three sections: Pregnancy, Lactation, and Females and Males of Reproductive Potential.

Some older, smaller studies suggested a possible, though inconsistent and controversial, link between early pregnancy amoxicillin use and oral clefts. However, larger, more rigorous modern studies have found no association with major birth defects.

Yes, amoxicillin is generally considered safe during breastfeeding. It is excreted into breast milk in very low levels and is considered compatible with breastfeeding by the American Academy of Pediatrics.

Side effects for a breastfed infant are rare and typically mild, but can include diarrhea, rash, or oral thrush. Monitoring the infant is recommended, and any concerns should be discussed with a doctor.

A pregnant woman prescribed amoxicillin should take the full course as directed by her doctor. It's important to treat the underlying infection, as the risks of an untreated infection often outweigh the minimal risks of this medication.

Yes, other penicillins (like penicillin V and ampicillin), cephalosporins (like cephalexin), and some macrolides (like azithromycin) are also commonly prescribed and considered generally safe during pregnancy.

An untreated bacterial infection can pose serious risks to both the pregnant person and the fetus, potentially leading to a more severe illness, preterm delivery, or other complications. Treating the infection promptly is crucial.