Amoxicillin is generally considered safe during pregnancy. It belongs to the penicillin family of antibiotics, which has one of the longest and most reassuring safety records of any drug class used in pregnant women. The FDA states that published clinical studies have not identified an association between amoxicillin exposure during pregnancy and major birth defects, miscarriage, or adverse maternal or fetal outcomes.
What the Safety Data Shows
Penicillins, including amoxicillin, are among the most studied medications in pregnancy. A large population-wide cohort study published in the American Journal of Obstetrics & Gynecology found no increased risk of congenital malformations following first-trimester exposure to the ten most commonly prescribed antibiotics, with penicillins used as the safety benchmark. The researchers noted that their findings came with “a high degree of precision,” meaning the study was large enough to detect even small risks if they existed.
Animal studies also show no evidence of fetal harm from amoxicillin. This combination of human epidemiological data and animal data is why medical organizations consistently place amoxicillin among the preferred antibiotics when pregnant women need treatment.
How It Compares to Other Antibiotics
Not all antibiotics share amoxicillin’s safety profile. A study in the Canadian Medical Association Journal examined antibiotic use and miscarriage risk across thousands of pregnancies. Several antibiotic classes were linked to higher rates of spontaneous abortion: quinolones (like ciprofloxacin) carried roughly 2.7 times the risk, tetracyclines about 2.6 times, and clarithromycin about 2.4 times. Penicillins, by contrast, were used as the reference group precisely because they showed no increased risk. In one subgroup analysis, quinolone exposure was associated with nearly nine times the miscarriage risk compared to penicillin use among women with urinary tract infections.
This is why medical guidelines actively recommend switching pregnant women to amoxicillin from riskier antibiotics when possible. ACOG, for example, advises that pregnant women being treated with ciprofloxacin should switch to amoxicillin once the infection is confirmed to respond to penicillin.
Common Reasons It’s Prescribed in Pregnancy
Urinary tract infections are one of the most frequent reasons pregnant women receive amoxicillin. Pregnancy increases UTI risk due to changes in the urinary tract, and even infections without symptoms (asymptomatic bacteriuria) are typically treated because untreated UTIs can lead to kidney infections and preterm labor. A standard course runs 5 to 7 days.
Amoxicillin is also prescribed for respiratory infections, dental infections, ear infections, and skin infections during pregnancy. The conditions themselves, if left untreated, often pose a greater risk to the pregnancy than the antibiotic does.
How Pregnancy Affects the Drug
Your body processes amoxicillin differently when you’re pregnant. Blood volume increases significantly, kidneys filter faster, and the overall volume of fluid in your body expands. Research published in Antimicrobial Agents and Chemotherapy found that amoxicillin clearance rates in pregnant women are notably high, meaning the drug moves through your system more quickly than it would outside of pregnancy. This is why your provider may adjust the dose or frequency. Taking it exactly as prescribed matters more than usual because the drug leaves your bloodstream faster.
Potential Effects on Infant Gut Health
While amoxicillin does not cause birth defects, newer research is exploring subtler effects. A 2024 study found that prenatal amoxicillin exposure in animal models disrupted the gut bacteria composition in offspring, particularly reducing a bacterial group called Lachnospiraceae. This shift was linked to lower levels of a fatty acid involved in brain development and, in the animal models, to behavioral changes resembling depression. Supplementing with the missing bacteria or fatty acid reversed these effects in the study.
Some epidemiological data has also suggested associations between prenatal antibiotic exposure broadly and conditions like childhood asthma or mood disorders, though these are correlations from observational studies and don’t prove that amoxicillin caused the outcomes. The key takeaway is not that amoxicillin should be avoided, but that it should be used when genuinely needed rather than for viral infections or minor illnesses where antibiotics won’t help anyway.
Side Effects for the Mother
The side effects of amoxicillin during pregnancy are the same ones anyone might experience: diarrhea, nausea, and yeast infections. Pregnancy already increases your susceptibility to vaginal yeast infections because of hormonal changes, so adding an antibiotic can make that more likely. Eating yogurt or taking a probiotic alongside the course may help, though you should space probiotics a couple of hours away from the antibiotic dose.
Allergic reactions are the most serious concern. If you’ve had a rash, hives, or breathing difficulty with any penicillin-type antibiotic before, amoxicillin is off the table. True penicillin allergy affects a small percentage of the population, though many people who believe they’re allergic can actually tolerate penicillins safely. Allergy testing during pregnancy is considered safe by the CDC.
If You’re Allergic to Penicillin
Options narrow when you can’t take penicillin-based antibiotics during pregnancy. For most infections, your provider can choose from other pregnancy-compatible antibiotics depending on the type of infection. For certain conditions, though, penicillin is irreplaceable. Syphilis during pregnancy, for instance, has no proven alternative treatment. In those cases, the CDC recommends referral to an allergist for desensitization, a supervised process that temporarily allows your body to tolerate the drug.
If you’ve been told you have a penicillin allergy but the reaction was mild or happened in childhood, it’s worth discussing allergy testing with your provider. Up to 90% of people labeled as penicillin-allergic turn out to tolerate it when formally tested, which opens the door to the safest antibiotic options during pregnancy.