In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. This sheet talks about whether exposure to St. John’s Wort may increase the risk for birth defects over that background risk. This information should not take the place of medical care and advice from your health care provider.

What is St. John’s Wort?

St. John’s Wort is an herbal medication most commonly used to treat mild or moderate depression. The active ingredients and components of St. John’s Wort can vary widely and are altered by the harvesting, drying process, and storage of the plant material.

In the United States, St. John’s Wort is characterized as a dietary supplement. Unlike a prescription medication, it is not regulated by the Food and Drug Administration and does not have set standards for preparation, safety, or degree of effectiveness. For information on supplements in general, please see our fact sheet on Herbal Products at:

It has been noted that St. John’s Wort might lower the effectiveness of birth control.

I am taking St. John’s Wort, but I would like to stop taking it before becoming pregnant. How long does St. John’s Wort stay in your body?

Individuals break down medicines at different rates. St. John’s Wort is a long-acting agent, with a half-life of 26.5 hours (half-life is the amount of time it takes your body to eliminate half of the dose of the medication). It is likely that levels of St. John’s Wort would be low after one week, but there are no studies looking at this. It’s recommended that you talk to your health care provider to understand the benefits of taking this medication for your specific situation, and any possible concerns with not taking it.

Should I stop taking St. John’s Wort during my pregnancy?

It’s recommended that you talk to your health care provider before you stop taking this supplement. Not enough research has been done on the use of St. John’s Wort in pregnancy. More research is needed to understand the possible effects of St. John’s Wort on a developing baby. In some situations where a woman is significantly depressed, her health care provider may choose to prescribe an antidepressant that has been better studied in pregnant women.

Can taking St. John’s Wort during my pregnancy cause birth defects?

A small study that looked at 49 pregnancies with at least first trimester exposure to St. John’s Wort did not find an increase in birth defects compared to women taking prescription antidepressant medication. Larger studies are needed to confirm this finding.

Can taking St. John’s Wort during my pregnancy cause other kinds of problems?

St. John’s Wort causes increased uterine muscle tone in laboratory animals, and could potentially cause uterine contractions. While one small study found higher rates of miscarriage in pregnancies where the mothers were taking St. John’s Wort compared to another antidepressant or no antidepressant, the rates between these three groups were not significantly different.

There are no studies looking at exposure to St. John’s Wort and withdrawal symptoms or effects on the baby’s behavior or development. Any possible associated risks are unknown. The tannic acid present in St. John’s Wort may prevent absorption of iron, an important mineral for pregnant women and their babies.

Can I take St. John’s Wort while breastfeeding?

In a small study of 5 breastfeeding mothers of full-term older infants (10-22 weeks), the amount of St. John’s Wort that the infants received through breast milk was found to be small. The mothers reported no negative effects in their infants. Another study, involving 33 women who took St. John’s Wort and breastfed, found a higher frequency of side effects (colic and drowsiness) when compared to a group of infants whose mothers had depression but were not taking St John’s Wort. The infants did not require medical treatment.

St. John’s Wort is a long-acting medication, and any amount ingested by the infant would be expected to remain for a long time. Until more is known about St. John’s Wort, speak with your health care provider about prescription antidepressants that have been better studied in breastfeeding women, and all your choices for breastfeeding.

What if the father of the baby takes St. John’s Wort?

One study found that large amounts of St. John’s Wort added directly to semen decreased sperm movement and viability. Effects on male fertility from taking St. John’s Wort have not been evaluated but there are currently no human data to suggest that use of St. John’s Wort by the father would negatively affect the sperm or increase the risk for birth defects. In general, exposures that fathers have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet on Paternal Exposures at

Selected References:

  • Barrett B, et al. 1999. Assessing the risks and benefits of herbal medicine: An overview of scientific evidence. Altern Ther Health Med 5(4):40-49.
  • Fetrow CW amd Avila JR. 1999. Professional’s Handbook of Complementary and Alternative Medicines. Springhouse, PA: Springhouse Corporation.
  • Klier CM, et al. 2006. St. John’s wort (Hypericum perforatum) and breastfeeding: plasma and breast milk concentrations of hyperforin for 5 mothers and 2 infants. J Clin Psychiatry. 67(2):305-309.
  • Lee A, et al. 2003. The safety of St. John’s Wort (Hypericum perforatum) during Breast-feeding. J Clin Psychiatry 64(8):966-968.
  • Miller LG. 1998. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med 158(20): 2200-2211.
  • Moretti ME, et al. 2009 Evaluating the safety of St. John’s Wort in human pregnancy. Reprod Toxicol. 28(1):96-99.
  • Nordeng H and Havnen GC. 2004. Use of herbal drugs in pregnancy: a survey among 400 Norwegian women. Pharmacoepidemiol Drug Safety 13:371-380.
  • Ondrizek RR, et al. 1999. Inhibition of human sperm motility by specific herbs used in alternative medicine. J Assist Reprod Genet 16(2):87-91.
  • Shiplochliev T. 1981. Extracts from a group of medicinal plants enhancing uterine tonus. Vet Med Nauki 18:94-98.