This sheet is about exposure to metronidazole in pregnancy and while breastfeeding. This information should not take the place of medical care and advice from your healthcare provider.
What is metronidazole?
Metronidazole is an antimicrobial that has been used to treat infections. Metronidazole has been used to treat some types of vaginal infections. It is available in oral, rectal, topical, vaginal and intravenous (I.V.) forms. Metronidazole has been sold under brand names such as Flagyl®, Metrogel® Metrolotion® or Noritate®.
Sometimes when people find out they are pregnant, they think about changing how they take their medication, or stopping their medication altogether. However, it is important to talk with your healthcare providers before making any changes to how you take this medication. Your healthcare providers can talk with you about the benefits of treating your condition and the risks of untreated illness during pregnancy.
I take metronidazole. Can it make it harder for me to get pregnant?
Based on the studies reviewed, it is not known if metronidazole can make it harder to get pregnant.
Does taking metronidazole increase the chance for miscarriage?
Miscarriage is common and can occur in any pregnancy for many different reasons. Based on studies reviewed, it is unlikely that metronidazole would greatly increase the chance of a miscarriage. There is one large study that looked at over 4000 pregnancies with exposure to metronidazole early in pregnancy that did not find an increased chance for miscarriage. One small study with 53 pregnancies with exposure to metronidazole reported a greater chance for miscarriage. It is not clear if the miscarriage risk was from the medication or related to the underlying infection that was being treated.
Does taking metronidazole 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. Based on studies reviewed, metronidazole is not expected to increase the chance for birth defects.
Does taking metronidazole in pregnancy increase the chance of other pregnancy related problems?
Based on the studies reviewed, metronidazole is not expected to increase the chance for 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).
Does taking metronidazole in pregnancy affect future behavior or learning for the child?
Studies have not been done to see if metronidazole can cause behavior or learning issues for the child.
Breastfeeding while taking metronidazole:
Metronidazole passes into breastmilk. The amount of metronidazole that passes into breastmilk can depend on the dose and how the medication is taken (by mouth, by IV, vaginally, or topically). With oral or IV use, the amount of metronidazole in breast milk can be close to the amount of medication that would be given to treat infants. Amounts in breastmilk might be lower with vaginal or topical use. Possible side effects in breastfed infants include loose stools, or a yeast infection (diaper rash or thrush). There are also reports of babies who were exposed to metronidazole in breastfeeding without reported side effects. If you suspect the baby has any symptoms (loose stools, diaper rash, or thrush), contact the child’s healthcare provider.
Some metronidazole product labels suggest talking with your healthcare provider before using metronidazole while breastfeeding. Your healthcare provider can talk with you about the benefits of using this medication to treat your medical condition versus using a different treatment. Be sure to talk to your healthcare provider about all of your breastfeeding questions.
If a male takes metronidazole, could it affect fertility (ability to get partner pregnant) or increase the chance of birth defects?
Based on the studies reviewed, it is not known if metronidazole could affect male fertility or increase the chance of birth defects in a partner’s pregnancy. In general, exposures that fathers or sperm donors have are unlikely to increase the risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
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OTIS/MotherToBaby encourages inclusive and person-centered language. While our name still contains a reference to mothers, we are updating our resources with more inclusive terms. Use of the term mother or maternal refers to a person who is pregnant. Use of the term father or paternal refers to a person who contributes sperm.