Weed is a drug derived from the plant Cannabis sativa. It’s used for recreational and medicinal purposes.

What a mom-to-be puts on her skin, eats, and smokes affects her baby. Weed is one substance that can potentially impact a developing baby’s health.

What is weed?

Weed (also known as marijuana, pot, or bud) is the dried portion of the Cannabis sativa plant. People smoke or eat weed for its effects on the body. It can cause euphoria, relaxation, and enhanced sensory perception. In most states, recreational use is illegal.

Weed’s active compound is delta-9-tetrahydrocannabinol (THC). This compound can cross a mother’s placenta to get to her baby during pregnancy.

But weed’s effects during pregnancy can be difficult to determine. This is because many women who smoke or eat weed also use substances like alcohol, tobacco, and other drugs. As a result, it’s tough to say which is causing a problem.

What’s the prevalence of weed use in pregnancy?

Weed is the most commonly used illicit drug during pregnancy. Studies have tried to estimate the exact number of pregnant women who use weed, but results vary.

According to the American Congress of Obstetricians and Gynecologists (ACOG), 2 to 5 percent of women use weed during pregnancy. This number goes up for certain groups of women. For example, young, urban, and socioeconomically disadvantaged women report higher rates of use that reach up to 28 percent.

What are the potential effects of using weed while pregnant?

Doctors have linked weed use during pregnancy with increased risk for complications. These may include:

  • low birth weight
  • premature birth
  • small head circumference
  • small length
  • stillbirth

What are the potential effects of using weed after a baby is born?

Researchers mostly study the effects of weed use during pregnancy on animals. Experts say exposure to THC can affect a baby’s brain development.

Babies born to mothers who smoke weed during pregnancy don’t have serious signs of withdrawal. However, other changes may be noted.

Research is ongoing, but a baby whose mother used weed during pregnancy may have problems as they get older. The research isn’t clear: Some older research reports no long-term developmental differences, but newer research is showing some problems for these children.

THC is considered a developmental neurotoxin by some. A child whose mother used weed during pregnancy may have trouble with memory, attention, controlling impulses, and school performance. More research is needed.

Misconceptions about weed use and pregnancy

The growing popularity of vape pens has led weed users to switch from smoking the drug to “vaping.” With vape pens, users inhale a liquid vapor instead of smoke.

Many pregnant women mistakenly think vaping or eating weed doesn’t harm their baby. But these preparations still have THC, the active ingredient. As a result, they can harm a baby. We just don’t know if it’s safe, and therefore is not worth the risk.

What about medical marijuana?

Several states have legalized weed for medical use. It’s often referred to as medical marijuana. Expectant moms or women wishing to become pregnant may wish to use weed for medical purposes, like relieving nausea.

But medical marijuana is difficult to regulate during pregnancy.

According to the ACOG, there are no:

  • standard dosages
  • standard formulations
  • standard delivery systems
  • Food and Drug Administration-approved recommendations regarding use in pregnancy

For these reasons, women hoping to become pregnant or who are pregnant are advised against using weed.

Women can work with their doctors to find alternative treatments.


Doctors recommend against using weed during pregnancy. Because types of weed can vary and chemicals can be added to the drug, it’s even harder to say what’s safe. Plus, weed use has been associated with increased risk for problems during pregnancy, in the newborn, and later on in a baby’s life.

If you’re pregnant or thinking of becoming pregnant, be honest with your doctor. Tell them about your use of weed and any other drugs, including tobacco and alcohol.

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I smoke pot a few times a week, and then I found out I was two months pregnant. Is my baby going to be OK?

Anonymous patient


When a pregnant woman smokes marijuana, it increases her exposure to carbon monoxide gas. This can affect the oxygen the baby receives, which could impact the baby’s ability to grow. While this doesn’t always happen in babies whose mothers smoked marijuana, it can increase a baby’s risk. If you’re pregnant or thinking of becoming pregnant and use marijuana regularly, talk to your doctor about ways you can quit. This will ensure the greatest safety for your little one.

Rachel Nall, RN, BSN

Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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Rachel Nall is a Tennessee-based critical care nurse and freelance writer. She began her writing career with the Associated Press in Brussels, Belgium. Although she enjoys writing about a variety of topics, healthcare is her practice and passion. Nall is a full-time nurse at a 20-bed intensive care unit focused primarily on cardiac care. She enjoys educating her patients and readers on how to live healthier and happier lives.