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There are no studies to indicate that valacyclovir is dangerous during pregnancy. For instance, one small study introduced the similar antiviral acyclovir to about 750 pregnant individuals and found it did not change the occurrence rate of birth defects. 

In animal studies, it did not affect the fetus even at ten times human plasma levels. 

Valacyclovir and Breastfeeding

Testing did find a small amount of acyclovir, the chemical valacyclovir converts to, in breast milk. The FDA states that nursing parents may take valacyclovir if necessary but that they and their babies should be monitored closely. The Centers for Disease Control and Prevention recommends it only be used for severe genital herpes, though. 


Is valacyclovir safe during the first trimester?

There is no indication that it is dangerous to take during the first trimester, but few human studies exist. Animal studies found it to be safe, though. 

Is it safe to take valacyclovir while pregnant?

More studies are necessary to be sure it is safe for pregnant people. One human study found it did not affect the fetus, and animal studies indicate it is safe, as well. 

Does valacyclovir cause birth defects?

One study gave this drug to about 750 people during their first trimester. They found it did not increase birth defects in the participants, but more testing is necessary to be sure of its safety. 

Are antiviral drugs safe during pregnancy?

It depends upon the medication. Valacyclovir appears to be safe, based on limited clinical testing. For other antivirals, more tests are necessary to confirm this idea, though.  Always consult your doctor before taking any medications or supplements while pregnant.

Can Valtrex cause miscarriage?

There is no indication that Valtrex will cause a miscarriage, although studies are somewhat limited on the subject. 

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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