To learn more about cannabis, read the previous part — Cannabis Use by a Pregnant Woman.

Article updated June 1, 2023.

Many potential effects of cannabis use during pregnancy exist. Like for tobacco, cannabis use by a pregnant woman can affect the fetus and lead to health problems. Cannabis, like nicotine, constricts blood vessels (narrowing the vessels) which can limit the transmission of nutrients and oxygenation to a baby in full growth. Furthermore, second-hand smoke isn’t danger-free. Cannabis intolerance can lead to acute abdominal pain, which ceases only when the drug is stopped. Cannabis toxins are transported by the pregnant woman’s blood to the fetus, and can also be found in breast milk.

Heavy use of cannabis during pregnancy can mean that the drug invades the developing baby’s brain and impacts its normal development (cognitive and behavioural development). Cannabis use can also have a negative impact on breast milk production by inhibiting prolactin secretion.

Potential impacts on the pregnancy:

  •    Miscarriage risk (spontaneous abortion)
  •    Premature labour risk (if consumed heavily and regularly)

Possible effects on the fetus:

 If the pregnant woman uses both tobacco and cannabis, the impact on the baby is increased.

At birth:

  • Smaller head circumference (smaller cranial perimeter)
  • Growth delays
  • Low birth weight
  • Sleep disorders
  • Deprivation or withdrawal symptoms (trembling, irritability, slower reflexes, less reactive)
  • May have a cognitive impairment

Longer term (child or adolescent):

The brain develops until the age of 20 and can be influenced at any time. Children aren’t less intelligent, but effects may show up at different times over their lives, sometimes between 10 and 15 years:

  • A lowering:

        – Of memory capacity (memory problems)

        – Of concentration capacity (attention disorder)

        – Of reasoning and problem-solving skills

  • Hyperactivity
  • Learning and behavioural disorders (impulsivity)
  • Mental health problems, mood issues (anxiety, depression)
  • Increased risk of addiction problems in the future

To read the last part of this article, go to Fathers, Cannabis and Pregnancy.