Can azithromycin affect the baby? A detailed look at safety in pregnancy and breastfeeding

October 12, 2025 •

3 min read

According to studies, azithromycin is a frequently prescribed antibiotic for treating infections during pregnancy, such as chlamydia. However, conflicting study results and the need for medical assessment raise the critical question: can azithromycin affect the baby?

Quick Summary

Azithromycin is often considered generally safe during pregnancy and breastfeeding when prescribed by a doctor, especially when the benefits of treating an infection outweigh the risks. Some studies report conflicting outcomes regarding fetal harm, but the overall evidence is not conclusive. Low amounts of the drug pass into breast milk, with minimal harm anticipated.

Key Points

Benefit vs. Risk: Treating a maternal infection is crucial, as untreated infections pose a higher risk to the baby than a medically necessary dose of azithromycin.
Conflicting Evidence: Some studies show conflicting results on potential risks like congenital malformations or miscarriage, but no conclusive evidence proves a causal link.
Breastfeeding Considerations: Small amounts of azithromycin pass into breast milk, and infants should be monitored for mild gastrointestinal side effects.
Monitoring is Key: In infants, there is a very low and debated risk of infantile hypertrophic pyloric stenosis associated with macrolide use in early breastfeeding.
Doctor's Discretion: A healthcare provider must weigh the individual benefits and risks, considering the specific infection and gestational stage.
Preferred Option: For certain conditions like chlamydia in pregnant women, CDC guidelines list azithromycin as a recommended treatment.

Understanding Azithromycin's Role During Pregnancy

Azithromycin, a macrolide antibiotic, is commonly used for bacterial infections. Untreated infections during pregnancy can seriously harm both the mother and fetus, potentially leading to issues like preterm birth and neonatal infections. Healthcare providers must assess the risks of antibiotic exposure against the dangers of not treating an infection. The CDC recommends azithromycin as a primary treatment for chlamydia in pregnant women.

Conflicting Evidence and Potential Concerns

Despite decades of use in pregnant patients, some studies have presented conflicting data on azithromycin's fetal safety. A review indicated that while most studies don't show a link to major birth defects, some observational studies hinted at possible associations with increased risks of spontaneous miscarriage, major congenital malformations, and cardiovascular issues. However, the review also noted that other studies found no such links, highlighting the need for more rigorous research.

Observational studies have limitations and cannot always fully account for factors like maternal illness or other medications. An observed association might be a correlation, not a direct cause, with the infection itself potentially being the root of a poor pregnancy outcome.

Spontaneous Miscarriage: Limited evidence suggests a possible link between azithromycin use early in pregnancy and increased miscarriage risk.
Infantile Hypertrophic Pyloric Stenosis (IHPS): Some evidence points to a low risk of IHPS with maternal macrolide use during early breastfeeding, although this link is debated in meta-analyses.
Fetal Growth and Birth Weight: While some studies have suggested a possible link to low birth weight and preterm birth, definitive evidence is lacking.

Breastfeeding and Azithromycin

Small amounts of azithromycin pass into breast milk. Breastfeeding mothers should watch for potential gastrointestinal effects in their infant.

Potential infant side effects: Monitor for diarrhea, vomiting, or skin rash.
Infant gastrointestinal flora: The antibiotic may alter the infant's gut flora, potentially leading to candidiasis.
Benefits of breastfeeding: The benefits of breastfeeding generally outweigh the minimal risks associated with azithromycin use.

The Risks of Not Treating an Infection

Ignoring a bacterial infection during pregnancy poses greater risks than taking a necessary antibiotic. Untreated infections can lead to serious complications:

Preterm labor and birth
Low birth weight
Birth defects
Stillbirth or neonatal death
Serious illness or long-term disabilities for the baby

Comparison of Antibiotics During Pregnancy

When selecting an antibiotic during pregnancy, doctors choose the safest and most effective option. Here's a comparison of azithromycin with other common antibiotics:


Feature	Azithromycin	Penicillins (e.g., Amoxicillin)	Tetracyclines (e.g., Doxycycline)	Erythromycin (Another macrolide)
Pregnancy Category	Generally considered safe; some conflicting data on rare risks.	Generally safe and a first choice.	Contraindicated due to effects on fetal bone and tooth development.	May cause more GI side effects than azithromycin; conflicting data on safety.
First Trimester Use	Used when needed, particularly for chlamydia. Conflicting data on very rare malformations.	Considered safe in all trimesters.	Avoided after the fifth week.	Often used, but alternatives might be preferred due to potential side effects.
Breastfeeding Safety	Passes in small amounts; monitor for infant GI issues.	Generally safe and compatible with breastfeeding.	Generally avoided due to low levels in breast milk.	Passes into breast milk; monitor for GI side effects.
Key Risks	Conflicting reports on rare birth defects or miscarriage; debated link to IHPS in early nursing period.	Primarily allergic reactions; generally low risk for baby.	Tooth discoloration, bone development issues in fetus.	Higher GI upset risk for mother; some concerns re: IHPS (similar to azithromycin).

The Role of Medical Guidance

A doctor's consultation is vital to balance treating a maternal infection and minimizing medication risks. They will consider your history, the infection, and gestational age to determine the safest and most effective treatment. The aim is to use the safest drug at the safest dose.

Conclusion

While some observational studies present conflicting evidence, azithromycin is generally considered safe during pregnancy and breastfeeding when prescribed by a healthcare provider. The potential, unconfirmed risks of azithromycin are typically outweighed by the known, significant risks of untreated maternal infections. The benefits of effective treatment for both mother and baby usually exceed possible, unproven risks. Given its long half-life, azithromycin use requires careful monitoring, and any concerns should be discussed with your doctor.

For further information, consult the National Institutes of Health research on azithromycin in pregnancy: Use of Azithromycin in Pregnancy: More Doubts than Certainties.

Frequently Asked Questions

Yes, when medically necessary, azithromycin is generally considered safe during pregnancy. However, like all medications, it is used only when a healthcare provider determines that the benefit of treating the infection outweighs the potential risks.

Multiple studies investigating azithromycin use in pregnancy have yielded conflicting results regarding birth defects. While some observational data has shown possible associations with rare malformations, definitive evidence is lacking, and many studies show no significant association.

Yes, breastfeeding is generally considered safe while taking azithromycin, provided your baby is healthy and your doctor gives the OK. Only small amounts of the drug pass into breast milk, and side effects in infants are rare.

Potential risks to the baby while breastfeeding on azithromycin include mild gastrointestinal upset, diarrhea, rash, or oral thrush. Some epidemiologic evidence suggests a debated link to infantile hypertrophic pyloric stenosis, a condition that is extremely rare and primarily a concern in the first two weeks after birth.

Untreated infections during pregnancy pose serious risks to both mother and baby, including preterm birth, low birth weight, birth defects, and stillbirth. The risks of not treating an infection are often far greater and more certain than the unconfirmed risks of azithromycin.

Azithromycin is used in the first trimester when indicated, particularly for infections like chlamydia. Some observational studies have shown conflicting results regarding early exposure and miscarriage, but no significant association with major birth defects has been definitively established.

No, azithromycin is not the only option. Depending on the infection, other antibiotics, such as penicillins (e.g., amoxicillin) and cephalosporins, are often considered first-line and are generally safe for use in pregnancy.

If you are pregnant and suspect you have an infection, consult your healthcare provider immediately. They will determine the safest and most effective treatment plan, taking into account the specific infection and your overall health.