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Is It Safe to Use Erythromycin During Pregnancy?

By M. Walker
Updated Feb 19, 2024
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It is generally considered safe to take erythromycin during pregnancy because there is minimal risk of harmful effects to the developing fetus. Erythromycin is placed in Pregnancy Category B by the Food and Drug Administration (FDA), which means that animal testing of erythromycin during pregnancy has found no significant risk to the fetus. While no full-controlled human studies have been conducted, no significant teratogenic, or harmfully abnormal, effects have been found in humans. Taking a specific form of erythromycin called erythromycin estolate during pregnancy, however, has been found to increase the possibility of hepatotoxicity, or liver damage to the mother, and it should only been used when a clear need has been demonstrated.

During an animal study, female rats were given erythromycin during pregnancy until after weaning had been completed. In this study, no harmful or teratogenic effects were observed, even when the rats were given erythromycin for the entire mating process as well as during pregnancy and weaning. This evidence supports the safety of erythromycin, but it cannot be fully applied to humans.

Several surveillance studies have observed various pregnancies and recorded data about the safety of using erythromycin during pregnancy. One study, the Collaborative Perinatal Project, observed 230 pregnancies in which the developing fetus had been exposed to erythromycin, out of a total of 50,282 pregnancies. No major link between erythromycin during pregnancy and any major developmental issues was observed.

Another surveillance study, which monitored 229,101 pregnancies of patients receiving Medicaid in the state of Michigan, found 6,972 cases of erythromycin use during pregnancy. From these pregnancies, 320 major birth defects were observed. While this number is slightly higher than the expected average of 297 defects, the study found no significant correlation between erythromycin use and resulting birth defects.

Erythromycin does cross the placental barrier and enters the fetal bloodstream in small amounts. Although the levels of erythromycin increase in the fetal bloodstream when the mother’s dosage increases, maternal erythromycin levels can vary during pregnancy, making it difficult to measure the degree of transmission. The levels in the fetal bloodstream are generally considered sufficiently low enough to not cause harmful effects.

A salt form of erythromycin, erythromycin estolate, should not be used during pregnancy. It has been found to increase the levels of serum glutamic-oxaloacetic transaminase (SGOT) in the bloodstream when taken during the second trimester of pregnancy. In one study, 10% of patients experienced these increased SGOT levels, indicating hepatotoxy had occurred. Once the use of erythromycin was stopped, these levels returned to normal, indicating that this is a temporary side effect of the drug.

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Discussion Comments
By burcinc — On May 02, 2013

Erythromycin might not harm the fetus, but sometimes it causes a type of hepatitis in the mother when used in pregnancy.

By bluedolphin — On May 01, 2013
@simrin-- What's the erythromycin dosage your doctor prescribed?

Low doses of eryhtromycin are absolutely safe during pregnancy. I used it when I was pregnant with my son and he came out perfect.

Erythromycin is an antibiotic and if the doctor prescribed it to you, it means you have an infection. I don't know what type of infection you have but I know that infections are dangerous for the fetus. If it is not treated and it spreads, it will harm your baby.

If I were you, I would speak to my doctor again about my concerns. Don't avoid this infection just because you don't want to take erythromycin. You may end up doing more harm than good.

By SteamLouis — On May 01, 2013

My doctor prescribed erythromycin for me and said it's safe to use even though I am two months pregnant. I don't care if it's considered safe, I'm not going to put my baby at risk. How can they say that this medication is safe during pregnancy when they know that it crosses the placenta?!

If I have to take the medication, I will wait at least a few more months until the baby's organs have fully developed.

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