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Antibiotics and pregnancy can feel like a tricky combo. You're dealing with a real infection that needs treatment, but you’re also growing a tiny human — and naturally, you're wondering what’s safe, what’s not, and how it all affects your baby.
The truth? Many antibiotics are totally safe to take during pregnancy, especially when prescribed for the right reasons and taken at the right doses. But not all are risk-free — some are linked to complications and should be avoided. Here’s what you need to know to feel informed (and less stressed) about taking antibiotics while pregnant.
Can a pregnant woman treat an infection?
Yes, absolutely — and in most cases, it’s essential.
Infections during pregnancy can be more than just uncomfortable. Some, like UTIs, can increase the risk of complications like kidney infections or even preterm labor if left untreated. Others, like strep throat, sinus infections, or bacterial vaginosis, can make you feel downright miserable and need to be treated to keep both you and your baby safe.
The good news is that bacterial infections respond well to antibiotics — and many antibiotics are safe to use during pregnancy. But it's never a DIY situation. Always check with your healthcare provider before starting (or stopping) any medication.
Will my antibiotics affect my baby?
This is one of the first questions that tends to pop up — and honestly, it makes total sense. You’re not just thinking about your own health anymore. The answer? It depends. Some antibiotics are completely safe and have been used for decades in pregnancy without issue. Others might raise red flags, especially if taken early on.
What really matters here is the type of antibiotic you’re prescribed, how long you’re taking it for, and when during pregnancy you’re using it. The first trimester — when all the important bits and pieces are forming — is when medications have the most potential to affect development. That’s why doctors are extra cautious in those early weeks.
It’s also worth knowing that many antibiotics do pass through the placenta. That doesn’t automatically mean danger, though. Some cross in small amounts and don’t appear to cause harm at all. Others can interfere with things like bone or tooth development — which is why they’re generally avoided once pregnancy is confirmed.
At the end of the day, it’s all about weighing the risk of the infection against the risk of the medication. Untreated infections can be risky too — even more so than the antibiotic used to treat them. As Dr. Caledonia Buckheit says, “When your provider recommends antibiotics, it’s because the benefits outweigh the risks!”
Do antibiotics pass through the placenta?
Yes, most do. The placenta is like a filter — but it’s not a brick wall. Many medications, including antibiotics, can cross the placenta to some degree and reach the developing fetus.
That doesn’t automatically make them dangerous. Some, like amoxicillin, cross in small amounts and haven’t been shown to cause harm. Others, like tetracyclines, can cross over and interfere with fetal bone and tooth development (they’re teratogenic).
That’s why doctors weigh the risks and benefits so carefully — and why certain antibiotics are preferred over others during pregnancy.
Which antibiotics are safe during pregnancy?
There’s no one-size-fits-all list, but the following antibiotics are generally considered safe for use during pregnancy when prescribed appropriately:
- Penicillins (like amoxicillin, ampicillin): These are widely used and well-studied during pregnancy.
- Cephalosporins (like cephalexin): Often used for UTIs and skin infections.
- Clindamycin: Safe in pregnancy and often used for bacterial vaginosis or dental infections.
- Erythromycin: Considered safe, although some forms (like erythromycin estolate) are avoided.
- Nitrofurantoin: Commonly used for UTIs — generally safe in the second and third trimesters, but often avoided late in the third trimester due to rare risk of hemolytic anemia in neonates with G6PD deficiency
- Fosfomycin: A single-dose antibiotic used for UTIs, considered low-risk during pregnancy.
Each of these has a solid track record, and most fall under FDA pregnancy categories B or C (meaning no evidence of harm in human studies or limited animal data with no clear risk). That said, the FDA now uses a more detailed “Pregnancy and Lactation Labeling Rule” (PLLR), so your doctor will consider the most up-to-date safety data.
What antibiotics are forbidden in pregnancy?
Some antibiotics should be avoided altogether while pregnant due to known risks to fetal development. These include:
- Tetracyclines (like doxycycline, tetracycline): Can cause permanent discoloration of your baby’s teeth and affect bone growth — and has been linked to a higher rate of pregnancy loss before 20 weeks.
- Fluoroquinolones (like ciprofloxacin, levofloxacin): Linked to cartilage damage in animal studies — generally not recommended.
- Trimethoprim (found in Bactrim): May interfere with folic acid, which is crucial in early pregnancy. Often avoided, especially in the first trimester.
- Streptomycin and kanamycin (types of aminoglycosides): Associated with hearing loss in the fetus.
- Macrolides, which can be used to treat some common bacterial infections, have been linked to major fetal malformations like heart and genital defects, and neurodevelopmental disorders. But, as Dr. Buckheit explains, “Azithromycin and erythromycin (except estolate) are generally considered safe; large population studies have not shown a significant increase in major congenital malformations with these. Erythromycin estolate is avoided due to maternal hepatotoxicity risk.”
What if you took antibiotics before knowing you were pregnant?
You’re not alone — this comes up a lot. In one study, up to 70% of people took some kind of medication (including antibiotics) before realizing they were pregnant. Most of the time, the body is incredibly resilient, and early exposure doesn’t cause harm.
Still, if you’re concerned, don’t panic — reach out to your doctor or a teratogen information service like MotherToBaby for more information. They can help assess the specific medication, dose, and timing.
Do antibiotics mess with your gut or your baby’s microbiome?
They might — but let’s not panic. Antibiotics are powerful because they wipe out bacteria, but the catch is they don’t always know the difference between the bad guys and the good ones. So while they’re busy treating your infection, they can also disrupt the healthy bacteria living in your gut. That’s totally normal and usually temporary, but during pregnancy, there’s an extra layer to think about.
Your microbiome — that whole ecosystem of bacteria in your body — plays a big role in digestion, immune health, and even mood. And research suggests that your baby starts developing their own microbiome during pregnancy, partly influenced by yours. So, yeah, changes to your gut bacteria might have some downstream effects on your baby’s gut too.
Some studies have linked certain antibiotics in pregnancy with a higher risk of things like childhood allergies or asthma. But the science isn’t settled, and correlation doesn’t equal causation. Just because an antibiotic may impact gut bacteria doesn’t mean it’s dangerous. In most cases, treating an infection quickly and effectively is the healthiest choice — for both of you.
If you’re worried about gut health, it’s worth having a conversation with your provider. You can support your microbiome with a diet high in fiber, including fruits, vegetables, and whole grains to support gut microbial diversity. Increasing intake of prebiotic-rich foods (e.g., onions, garlic, asparagus, bananas, whole grains) has been shown to support the maternal and infant gut microbiome. But again, don't let fear of microbiome shifts stop you from taking something you need. Your body — and your baby — are more resilient than you think.
What to remember about antibiotics and pregnancy
Here’s the bottom line: If you’re pregnant and dealing with an infection, getting the right treatment matters. Not only is it safe to treat infections during pregnancy — it’s often necessary. Certain antibiotics, like amoxicillin or cephalexin, have been used for years and are considered low-risk. Others, like tetracycline or ciprofloxacin, are best avoided because of known side effects. That’s why your provider will carefully choose the safest option based on your specific situation.
Yes, antibiotics can cross the placenta, and yes, they can influence your gut and your baby’s developing microbiome — but that doesn’t mean they’re harmful. When prescribed appropriately, they’re a powerful tool for protecting your health and your baby’s, too. The key is not to self-prescribe or use leftover meds from a previous illness. Always speak to your provider, ask the questions, and make decisions together.
A short course of antibiotics, when needed, is not something to feel guilty about. It’s a step toward healing. So if you’re sitting there with a prescription in one hand and a million questions in your head — you’re not alone. Ask for answers. Get support. And know that protecting your health is one of the most important things you can do during pregnancy.
Tassia O'Callaghan is an experienced content writer and strategist, having written about a vast range of topics from chemical regulations to parenting, for brands like Peanut App Ltd, Scary Mommy, Fertility Mapper, Tally Workspace, and Office Christmas. She's an advocate for realistic sustainable living, supporting small businesses (author of A-Z of Marketing for Small Businesses), and equity across all walks of life. Follow her on LinkedIn or TikTok, or see more of her work on Authory or her website.