Cannabis: Before, during and after pregnancy

Fast Facts

  • If you use cannabis and are pregnant or are planning a pregnancy, talk to your healthcare provider.
  • Using cannabis (marijuana, weed, pot) during pregnancy may increase your baby’s risk of developmental problems.
  • The chemicals in any form of cannabis (smoking, second-hand smoke, vapour, edibles, oils/creams) may be harmful for your baby.
It is not safe to use cannabis in pregnancy or when breastfeeding


Studies have shown that daily cannabis use is linked to:

  • Changes to the menstrual cycle
  • Low sperm count and poor sperm quality


Cannabis contains over 400 chemicals, including THC - the chemical that makes you feel “high”.

  • These chemicals can pass from your body to your baby when you are pregnant and may be harmful.

Cannabis smoke contains many of the same harmful chemicals as cigarette smoke.

  • Smoking lowers the supply of oxygen and nutrients to your baby.

Ask your healthcare provider about safer ways to treat nausea and vomiting during pregnancy.


A baby’s brain contains a lot of fat. THC is stored in fat and it could largely affect how your baby’s brain develops.

Research shows that cannabis in pregnancy may increase the risk of:

  • Pre-term birth
  • Low birth weight
  • Lower IQ scores
  • Impulsivity and hyperactivity in  childhood
  • Learning, memory and problem-solving difficulties in teens and later in life


Can cannabis affect my breastmilk?

  • Cannabis passes from your breastmilk to your baby. THC and other chemicals are stored in baby’s fat cells and brain for a long time.
  • Cannabis may make your baby drowsy and it could make it harder for your baby to latch properly. It may also affect your baby’s movement and responses.

Will it help if I “pump and dump” my breastmilk after using cannabis?

No. THC is stored in body fat and released into breastmilk for weeks. Pumping and throwing out your breastmilk shortly after using cannabis doesn’t mean your breastmilk won’t have THC in it the next time you feed your baby.

Cannabis and parenting

  • Never drive a car while impaired. It’s unsafe for you and for those riding in the car.
  • Second-hand cannabis smoke is harmful for all of us. It is best not to smoke or vaporize cannabis in your home or around your baby or children.
  • Cannabis use can affect your short-term memory, attention and reaction time. Parenting while impaired may reduce your ability to make good decisions and protect your child from harm. You may also miss your child’s cues for hunger, comfort or to play and learn.
  • Bed sharing is not safe. But bed sharing while high makes the risk of sleep-related deaths even higher. Place your baby to sleep alone on their back in their crib, cradle or bassinet.
  • Store your cannabis in a safe place so your children can’t reach it. If you think your child took any form of cannabis, get medical help right away. Call the Ontario Poison Centre at 1-800-268-9017 or call 911 immediately.
Until more is known about the short- and long-term effects of cannabis on your baby, it’s safest to avoid using cannabis while pregnant or breastfeeding.

For more information or help:

  • Talk to your healthcare provider
  • Visit
  • MotherToBaby (experts available by phone, email or live chat to discuss the risk or safety of medications, alcohol, herbal products and more during pregnancy and breastfeeding)
  • Here 24/7 (addiction, mental health and crisis services for Waterloo-Wellington): 1-844-437-3247
  • ConnexOntario (addiction, mental health and problem gambling services): 1-866-531-2600

Adapted from a resource produced by the City of Hamilton Public Health Services. Distributed by Wellington-Dufferin-Guelph Public Health.

Cannabis and pregnancy fact sheet page 1Cannabis and pregnancy page 2