Arizona regulations require that recommending physicians and dispensaries advise qualifying patients about any risks associated with the use of medical marijuana. So, as a clinician and a potential dispensary medical director, the question of what to advise female patients of child bearing age about the risk to the fetus, if any, of using marijuana during pregnancy is of real concern. The answer isn’t simple.

In Canada, qualifying patients may be legally prescribed a drug named Sativex, which contains THC (tetrahydrocannabinol) and CBD (cannabidiol), the two primary active ingredients in marijuana. One of the most respected and authoritative medical textbooks is “Harrison’s Textbook of Medicine.” In discussing THC and CBD in its digital edition, “Harrison’s Practice,” it states:

“Cannabinoids have been associated with reproductive toxicity. Animal studies indicate possible effects on fetal development and spermatogenesis. USE IN PREGNANCY IS CONTRAINDICATED. (Emphasis added.) Women of childbearing potential and males who are capable of causing pregnancy should use a reliable form of contraception for the duration of treatment and for 3 months following discontinuation.”

With respect to lactation, “Harrison’s Practice” states that THC and CBD enter breast milk and is thus contraindicated as well.

However, on the Sativex website, this contraindication of taking THC and CBD during pregnancy is not so blanket. It states that taking the drug during pregnancy is contraindicated “unless the potential risks to the fetus and/or embryo are considered to be outweighed by the benefit of treatment.”

But the foregoing contraindications and cautions are based primarily on animal studies, and many experts believe the risk of marijuana to the fetus is actually quite low based on human studies. In “Marijuana Myths, Marijuana Facts” by Morgan and Zimmer, it states that experts now agree that marijuana does not cause birth defects and, at worst, may be associated with slightly lower birth weights.

Indeed, most human studies have not found an increase in the risk for birth defects among babies exposed to marijuana while in the womb. In one study of 1246 women who reported occasional marijuana use during pregnancy, the frequency of birth defects was not elevated. A few studies have reported a very small increase in the risk for gastroschiasia, a rare defect in which the infant is born with intestines outside of the abdomen. There have been inconclusive studies that heavy use of marijuana during pregnancy may cause developmental brain problems in children exposed in utero.

So, what is a physician to advise female patients who are or may become pregnant? In my opinion, it would be advisable to exercise caution and follow the warning on the Sativex website, i.e. that marijuana should not be used during pregnancy unless any potential effects to the fetus are outweighed by the benefit of treatment. And with respect to women who are breast feeding, marijuana should definitely not be used.

Jason E. Gittman, MD, FCCP
[email protected]