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Is penicillin g safe during pregnancy?

Answered by MotherToBaby’s teratology specialists, quoted in full — including the questions most pages skip, like whether a father’s exposure matters.

By the pharmaranks editorial teamReviewed against the MotherToBaby fact sheet for penicillin g (OTIS, published via the NIH) sourcesUpdated Jul 21, 2026How we research

The questions people actually ask about penicillin g in pregnancy

Answered by MotherToBaby, the fact sheets written by the Organization of Teratology Information Specialists and published through the NIH. Quoted in full — we do not condense them.

I take penicillin G. Can it make it harder for me to get pregnant?

Studies have not been done to see if penicillin can make it harder to get pregnant.

Does taking penicillin G increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Taking penicillin G in pregnancy is not expected to increase the chance of miscarriage.

Does taking penicillin G increase the chance of birth defects?

Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. Multiple studies have looked at the use of penicillin G during pregnancy and have not reported an increased chance of birth defects.

Does taking penicillin G in pregnancy increase the chance of other pregnancy-related problems?

Penicillin G is not expected to cause other pregnancy-related problems, such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth).

Some people are allergic to penicillins. In very rare cases, penicillin G can cause anaphylaxis (severe allergic reaction where the body goes into shock). Anaphylaxis can cause trouble breathing, low blood pressure, dizziness or fainting, and nausea. Severe or uncontrolled anaphylaxis can affect blood flow to the fetus, which could affect the growth and development of the fetus. If you think you are allergic to penicillin, talk with your healthcare provider about this and the best way to treat your condition.

Does taking penicillin G in pregnancy affect future behavior or learning for the child?

Information from limited studies does not suggest that taking penicillin G during pregnancy can increase the chance of behavior or learning issues for the child.

If a male takes penicillin G, could it affect fertility or increase the chance of birth defects?

If you are taking penicillin G for an infection that can be transmitted to others by sexual contact (such as syphilis), it is important to treat your infection for your own health and for your partner’s health. Passing infections on to a partner who is pregnant might increase risks to a pregnancy. Your healthcare provider can talk with you about what steps can be taken to help prevent sexual transmission of infections to your partner.

Studies have not been done to see if penicillin G could affect male fertility (ability to get partner pregnant) or increase the chance of birth defects above the background risk. In general, exposures that fathers or sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/ .

Quoted from MotherToBaby Fact Sheets — Penicillin G, published June 2024. MotherToBaby states its fact sheets should not take the place of medical care and advice from your healthcare providers.

Breastfeeding is a separate question — what LactMed says about penicillin g

This is general reference information, not medical advice. Whether to take any medication in pregnancy is a decision for you and your prescriber; do not start or stop a drug on your own, because an untreated condition can also carry risk.