This sheet talks 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 used to treat infections. Metronidazole is commonly used to treat certain 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®.
I take metronidazole. Can it make it harder for me to get pregnant?
Based on the data available, it is not known if metronidazole can make it harder to become pregnant.
I just found out I am pregnant. Should I stop taking metronidazole?
Talk with your healthcare providers before making any changes to how you take your medication(s). It can be important to treat infections during a pregnancy. For some conditions, metronidazole may be the drug of choice.
Can metronidazole increase the chance for miscarriage?
Miscarriage can occur in any pregnancy. 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 study looked at 53 pregnancies with exposure to metronidazole. While the study did report 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. Older studies suggested an increased chance for various birth defects. However, more recent studies could find no evidence that using metronidazole during pregnancy increases the chance for birth defects. The current data do not support an increased chance for birth defects or other harmful effects on the baby.
Could taking metronidazole cause other pregnancy complications?
Based on the data available, metronidazole is not expected to increase the chance for other pregnancy complications. One study looked at over 900 women who had taken metronidazole sometime during their pregnancy and there was no increased chance for preterm delivery (birth before 37 weeks of pregnancy), low birth weight, or birth defects reported.
Does taking metronidazole in pregnancy cause long-term problems in behavior or learning for the baby?
Based on the data available, it is not known if metronidazole use in pregnancy can cause long-term problems.
What if I use metronidazole topically (on the skin) or vaginally?
When metronidazole is used on skin (topical preparations) only small levels are expected to be absorbed into the blood. If very little medication is in the blood, very little is expected to be able to affect a pregnancy. Vaginal use of metronidazole might result in more absorption of the medication into the body. Based on the data available, metronidazole is not expected to increase the chance for pregnancy complications.
Can I breastfeed while taking metronidazole?
Metronidazole gets into breast milk in relatively large amounts. However, the amount in breastmilk is below the dose given to treat young infants who were able to tolerate this drug. Amounts in breast milk would be lower with vaginal or topical use. If metronidazole is taken during breastfeeding, a nursing child might experience loose stools, especially when the drug is given directly into a vein (intravenously) to the person who is breastfeeding. Some babies might develop a yeast infection (diaper rash or thrush). There are also reports on breastfed babies without reported side effects. Be sure to talk to your healthcare provider about all of your breastfeeding questions.
I take metronidazole. Can it make it harder for me to get my partner pregnant or increase the chance of birth defects?
Based on the data available, it is not known if metronidazole can make it harder to get a partner pregnant or increase the chance for birth defects if taken by a father or sperm donor. 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/pdf/.
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