Skip to main content
Knowledge Exchange Portico Network
Centre for Addiction and Mental HealthKnowledge Exchange
Go Search


From: Exposure to Psychotropic Medications and Other Substances during Pregnancy and Lactation: A Handbook for Health Care Providers


Marijuana, hashish, hash oil, delta-9-tetrahydrocannabinol / cannabidiol (Sativex), delta-9-tetrahydrocannabinol (Marinol)

Street names

Marijuana: grass, weed, pot, dope (also used to refer to heroin), ganja, blunt, homegrown, reefer, bud, hydro, jay, spliff, Mary Jane (MJ), herb, doobie, simsemilla, chronic, bomb, joint

Hashish: hash

Hash oil: weed oil, honey oil

Cannabis is a drug prepared from the plant cannabis sativa, and can be smoked or ingested orally. It contains more than 400 chemicals, including delta-9-tetrahydrocannabinol (THC), the psychoactive component. When smoked, cannabis may pose some of the same risks associated with tobacco use.

Although cannabis is an illegal substance, in some circumstances a physician can prescribe its use through a Health Canada exemption. Clinical trials are done using government-grown cannabis, which is more standardized than cannabis sold on the street or grown in the home. Two legal pharmaceutical products containing THC are available in Canada.

Summary and Recommendations

  • Cannabis use during pregnancy should be decreased or avoided altogether.
  • Product monograms for Sativex and Marinol contraindicate the use of these products during pregnancy and breastfeeding.
  • Cannabis appears to be excreted into breast milk in moderate amounts. Cannabis exposure through breast milk has not been shown to increase risk to the baby, but no appropriate confirming studies are available. Women who cannot stop using cannabinoids should discuss the risks of breastfeeding while using cannabis against the overall benefits of breastfeeding. Breastfeeding babies should be closely monitored.
  • The effects of exposure to second-hand cannabis smoke in the baby’s environment should also be considered.

Fetal effects

Studies have demonstrated a small reduction in birth weight associated with cannabis use during pregnancy. A meta-analysis of 10 studies on maternal cannabis use and birth weight shows only a weak association. For babies born to women who used any cannabis at all, the mean birth weight was 48 grams less than the mean birth weight of the babies in the control groups. For babies born to women who used cannabis at least four times a day, the mean birth weight was 131 grams less than the mean birth weight of babies in the control groups.2

Major malformations

Chemicals in cannabis, including THC, cross the placenta but cannabis has not been implicated as a human teratogen.1

Spontaneous abortion

Maternal cannabis use has not been associated with spontaneous abortion.

Neonatal effects

There are no reports of adverse neonatal effects resulting from a woman using cannabis during pregnancy.

Long-term effects on the child

Some studies have shown certain neurodevelopmental effects of prenatal exposure to cannabis; however, broader long-term developmental effects are unclear. In many studies, isolating the effect of cannabis from confounders (e.g., poverty, poor nutrition, unsafe housing, violence, the use of other drugs) is difficult.

Studies report that:

  • at age three, sleep disturbances occurred in children of women who smoked cannabis during pregnancy.3
  • at age 10, increased hyperactivity, impassivity, inattention and delinquency occurred in children from families with low-incomes exposed prenatally to cannabis.4
  • from age nine to 12, no deficits in intelligence, memory or attention were reported, but poorer visual problem-solving skills were indicated in children exposed prenatally to cannabis (i.e., the hypothesis is that executive function is negatively affected).5


While the passage of cannabis into breast milk has not been studied extensively, cannabis appears to be excreted in moderate amounts. A 1982 study6 found that 0.8 per cent of the maternal intake of one joint was ingested by an infant in one feeding. In women who used cannabis heavily, the milk-to-plasma ratio (i.e., levels in milk versus levels in maternal blood) was as high as 8:1.

THC is lipophilic and can accumulate in breast milk, theoretically affecting brain development. Possible effects on the baby include lethargy, less frequent and shorter feeding times, and decreased motor development at one year of age, particularly if exposure to cannabis was early in the post-partum period.7 The long-term effects of using cannabis while breastfeeding are unclear.

Withdrawal effects on the mother

Symptoms of withdrawal from cannabis use, if they occur, are usually mild and may include sleep disturbance, irritability and loss of appetite. Symptomatic and sup-portive care for the mother is suggested.

Effects of untreated illness

In specific cases, cannabis and pharmaceutical products containing THC may be prescribed with a Health Canada exemption for symptomatic treatment of certain conditions (e.g., multiple sclerosis, AIDS, cancer). No studies have been completed of the continued use of cannabis during pregnancy under these conditions. The official product monographs for Marinol8 and Sativex9 contraindicate the use of these products during pregnancy and while breastfeeding. These products are used as symptomatic treatment, not to treat the underlying illness, and other standard treatments are available.

Also, cannabis has been suggested as a treatment for hyperemesis gravidarum, a serious and potentially fatal condition. In one study, women using cannabis during pregnancy reported a significant decrease in nausea, but not in vomiting.10 In another study, 37 out of 40 women who used cannabis to treat “morning sickness” rated it either effective or extremely effective.11


  1. Zuckerman, B., Frank, D.A., Hingson, R., Amaro, H., Levenson, S.M., Kayne, H. et al. (1989). Effects of maternal marijuana and cocaine use on fetal growth. New England Journal of Medicine, 320 (12), 762–768.
  2. English, D.R., Hulse, G.K., Milne, E., Holman, C.D. & Bower, C.I. (1997). Maternal cannabis use and birth weight: A meta-analysis. Addiction, 92 (11), 1553–1560.
  3. Dahl, R.E., Scher, M.S., Williamson, D.E., Robles, N. & Day, N. (1995). A longitudinal study of prenatal marijuana use: Effects on sleep and arousal at age three years. Archives of Pediatrics and Adolescent Medicine, 149 (2), 145–150.
  4. Goldschmidt, L., Day, N.L. & Richardson, G.A. (2000). Effects of prenatal marijuana exposure on child behavior problems at age 10. Neurotoxicology and Teratology, 22 (3), 325–336.
  5. Fried, P.A. & Watkinson, B. (2000). Visuoperceptual functioning differs in 9- to 12-year-olds prenatally exposed to cigarettes and marijuana. Neurotoxicology and Teratology, 22 (1), 11–20.
  6. Perez-Reyes, M. & Wall, M.E. (1982). Presence of delta9-tetrahydrocannabinol in human milk. New England Journal of Medicine, 307 (13), 819–820.
  7. Astley, S. & Little, R.E. (1990). Maternal marijuana use during lactation and infant development at one year. Neurotoxicology and Teratology, 12 (2), 161–168.
  8. Solvay Pharma. (2006). Marinol (delta-9-tetrahydrocannabinol): Product monograph. Markham, ON: Author.
  9. Bayer Healthcare Pharmaceuticals. (2006). Sativex (delta-9-tetrahydrocannabinol / cannabidiol): Product monograph. Toronto: Author.
  10. Chandra, K., Ho, E. Sarkar, M., Wolpin, J. & Koren, G. (2003). Characteristics of women using marijuana in pregnancy and their reported effects on symptoms of nausea and vomiting of pregnancy: A prospective controlled cohort study. Journal of FAS International, 1, e13
  11. Westfall, R.E., Janssen, P.A., Lucas, P. & Capier, R. (2006). Survey of medicinal cannabis use among childbearing women: Patterns of its use in pregnancy and retroactive self-assessment of its efficacy against “morning sickness.” Complementary Therapies in Clinical Practice, 12, 27–33.

Exposure to Psychotropic Medications and Other Substances during Pregnancy and Lactation: A Handbook for Health Care Providers

General issues and background

Psychotropic medications and other substances: Properties, effects and recommendations


Index of drugs

Bookmark and Share