Is Azithromycin Safe in Pregnancy? What to Know

If a clinician has prescribed azithromycin, or you have seen it referred to as a “Z-Pak,” and you are pregnant or trying to conceive, it is reasonable to want to know what is understood about its safety. Azithromycin is a commonly used antibiotic, and it is sometimes used during pregnancy. This article gathers what leading sources report so you can talk it through with the clinician who manages your care. It is general education only and is not a substitute for that conversation.

What azithromycin is and what it treats

Azithromycin is an antibiotic in the macrolide family. It is used to treat a variety of bacterial infections, such as certain chest infections, strep throat, and ear, sinus, or skin infections, and it is often given as a short course. In pregnancy it is also used to treat specific infections, including chlamydia and some others. Like all antibiotics, it works against bacteria and does not treat viral illnesses such as colds or the flu. It is a prescription medicine, so the choice of antibiotic and the length of the course are decisions your clinician makes based on the infection.

What the guidance says about pregnancy

A helpful plain-language summary comes from MotherToBaby, a service of the non-profit Organization of Teratology Information Specialists, which reviews the published research on exposures in pregnancy.

Birth defects

MotherToBaby reports that most studies have not found an increased chance of birth defects when azithromycin is used in pregnancy, though a few studies have suggested it might increase the chance of some birth defects. Taken together, the reassurance is meaningful but not absolute, which is one reason the decision is individualized with your clinician. For context, about 3 in 100 babies in the general population are born with a birth defect regardless of any medicine.

Miscarriage, preterm birth, and birth weight

According to MotherToBaby, most studies on azithromycin and similar antibiotics have not reported an increased chance of miscarriage, and azithromycin is not expected to increase the chance of other pregnancy-related problems such as preterm delivery (birth before 37 weeks) or low birth weight. As always, an antibiotic is one piece of a larger clinical picture, and your provider weighs your specific infection and history.

Longer-term child development

MotherToBaby notes that one large study of more than 8,000 children did not find a significant increase in the chance of attention deficit hyperactivity disorder (ADHD) or autism spectrum disorder after azithromycin exposure. This kind of longer-term follow-up adds to the overall picture, although research in this area continues.

A note on old drug “categories”

You may see the old FDA A/B/C/D/X pregnancy letter categories quoted in older leaflets. Those letter grades have been retired. The FDA now uses a narrative labeling approach, sometimes called the Pregnancy and Lactation Labeling Rule (PLLR), that summarizes the actual evidence rather than assigning a single letter. If you find a letter grade quoted for azithromycin, treat it as outdated and rely on current guidance and your clinician.

The other side: untreated infection also carries risk

It is important not to let worry about medicines lead to leaving a real infection untreated. Bacterial infections in pregnancy, including some sexually transmitted infections, can affect both parent and baby if they are not treated. That is why clinicians often view an appropriate antibiotic as the safer choice compared with an untreated infection. Your provider can explain the benefit of treating your specific condition against any theoretical concern about the medicine, which is exactly the balance these decisions are meant to weigh.

Breastfeeding

MotherToBaby reports that short-term azithromycin use is generally considered compatible with breastfeeding, and that the antibiotic passes into breast milk in small amounts. Some studies have raised a question about a possible increase in a condition called pyloric stenosis when antibiotics are used in the first couple of weeks of breastfeeding, while other studies disagree. A breastfed baby may sometimes have loose stools or thrush. If you notice anything that concerns you, mention it to your clinician, especially for a newborn.

Do not start or stop on your own

A few principles are worth holding onto. Take only an antibiotic that has been prescribed for you and your current situation, rather than leftover pills or a course meant for someone else, because the wrong antibiotic can fail to treat the infection and contributes to resistance. Take the full course exactly as directed, even if you feel better, unless your prescriber tells you otherwise. And if you have any concern about an antibiotic during pregnancy, raise it with the prescriber rather than simply stopping, since a partly treated infection can be worse than none at all.

When to call your OB or a specialist

Reach out to your obstetric provider if you develop signs of infection such as fever or worsening symptoms, and before starting any antibiotic if you are pregnant. Seek prompt care for a severe allergic reaction, such as hives, swelling of the face or throat, or trouble breathing, which is an emergency. If you have a heart-rhythm condition, mention it, because macrolide antibiotics can occasionally affect heart rhythm. For questions about a specific medication exposure in pregnancy or breastfeeding, you can call MotherToBaby at 1-866-626-6847, a free service.

Frequently asked questions

Is azithromycin safe to take while pregnant? It is sometimes used in pregnancy, and MotherToBaby reports that most studies have not found an increased chance of birth defects. Whether it is right for you depends on your infection and history, so your clinician makes that call.

I took a Z-Pak before I knew I was pregnant. Should I worry? Most studies have not linked azithromycin to a higher chance of birth defects. Let your OB know what you took and when, and ask any follow-up questions there or through MotherToBaby.

Is azithromycin used to treat infections during pregnancy? Yes, it is used for certain infections in pregnancy, including chlamydia. Treating an infection is often safer than leaving it untreated, which is why your provider may recommend it.

Can I stop taking it once I feel better? Generally no. Stopping an antibiotic early can leave an infection partly treated. Finish the full course as prescribed unless your clinician advises otherwise.

Does azithromycin affect the baby’s development? MotherToBaby notes a large study did not find a significant increase in ADHD or autism after azithromycin exposure, though research continues. Discuss any specific concern with your provider.

Can I take azithromycin while breastfeeding? MotherToBaby reports short-term use is generally considered compatible with breastfeeding, with only small amounts in breast milk. Watch for loose stools or thrush and mention any concerns to your clinician, especially for a newborn.

Sources

• MotherToBaby (Organization of Teratology Information Specialists) — Azithromycin (Z-Pak) fact sheet.
• MedlinePlus, U.S. National Library of Medicine — azithromycin consumer drug information.
• U.S. Food and Drug Administration — azithromycin prescribing information.