Safety and efficacy of St. John's wort (hypericum) during pregnancy and lactation.

BACKGROUND: There is a lack of basic knowledge on the part of both clinicians and patients as to the indications for use and safety of herbal medicines in pregnancy and lactation. This is one article in a series that systematically reviews the evidence for commonly used herbs during pregnancy and lactation. OBJECTIVES: To systematically review the literature for evidence on the use, safety, and pharmacology of St. John's wort focusing on issues pertaining to pregnancy and lactation. METHODS: We searched 7 electronic databases and compiled data according to the grade of evidence found. RESULTS: There is very weak scientific evidence based on a case report that St Johns wort is of minimal risk when taken during pregnancy. There is in vitro evidence from animal studies that St John's wort during pregnancy does not affect cognitive development nor cause long-term behavioral defects, but may lower offspring birth weight. There is weak scientific evidence that St. John's wort use during lactation does not affect maternal milk production nor affect infant weight, but, in a few cases, may cause colic, drowsiness or lethargy. There is weak scientific evidence that St John's wort induces CYP450 enzymes, which may lower serum medication levels below therapeutic range; this may be of concern when administering medications during pregnancy and lactation. CONCLUSIONS: Caution is warranted with the use of St John's wort during pregnancy until further high quality human research is conducted to determine its safety. St John's wort use during lactation appears to be of minimal risk, but may cause side effects. Caution is warranted when using medications along with St John's wort.