What You Should Know About the Effects of Marijuana Use During Pregnancy and While Breastfeeding

Marijuana use is increasing among people in their childbearing years. It is the most frequently used illegal drug among pregnant people.

With the increase in the knowledge of potential medical benefits of marijuana, some people are turning to marijuana to treat the symptoms of pregnancy such as nausea or vomiting. 

However, marijuana use has some serious risks for the baby. Read on to learn how marijuana use may affect an unborn or breastfeeding baby.

How does marijuana affect pregnancy?

If you’re pregnant and use marijuana, it has effects on your baby. The chemicals in marijuana pass through the placenta to the baby during pregnancy. These can lead to complications in the pregnancy. They can also put these babies at risk for longer-term problems. 

Research on this area is limited. Most of what we know is from self-reported data and retrospective studies. We don’t have details yet on: 

• How much marijuana is harmful

• When use is most risky

• What types of marijuana formulations might be more dangerous than others

But what we do know so far is concerning — and pregnant people should be advised to avoid it. 

Can marijuana use harm an unborn baby?

Yes, marijuana use can cause harm to an unborn baby. It can have effects on the baby throughout the pregnancy, leading to higher rates of miscarriage and impaired fetal growth. 

During the second trimester (week 13 through week 27), the baby is developing it’s endocannabinoid system, and marijuana use during this time could disrupt that normal development.

Marijuana use during pregnancy has been associated with harms to the baby including:

• Restricted fetal growth 

• Higher risk of low birth weight and preterm birth

• Higher risk of stillbirth

• Brain development issues including learning and behavioral problems such as ADHD later in life

How you take marijuana matters 

Marijuana can be: 

• Smoked

• Vaped

• Ingested

• Sprayed

• Applied topically

Marijuana contains hundreds of chemicals including: 

• THC (tetrahydrocannabinol), the psychoactive chemical that is in the marijuana plant that causes a high

• CBD (cannabidiol), which does not cause a high 

Marijuana products contain different amounts of THC and CBD. We don’t really know what dosing or formulation might be most harmful for unborn babies. 

We do know, however, that smoking marijuana can have additional negative consequences, and that secondhand marijuana smoke can harm babies and children. 

Is it illegal to use marijuana while pregnant?

Marijuana is still in the most dangerous category of controlled substances in the U.S., alongside drugs such as heroin and ecstasy. 

While marijuana is illegal under federal law, state laws vary. Medical cannabis is available to patients in 33 states and the District of Columbia. Recreational cannabis is now legal in 11 states. 

Some states could consider drug use in pregnancy to be child abuse, and it could lead to loss of custody or other penalties.

Is there ever a safe scenario to use marijuana during pregnancy?

No. Marijuana is known to cause harm and should be avoided during pregnancy.

What if you’re pregnant and use marijuana for nausea?

It’s important to know that there are serious risks of marijuana use to your unborn baby. There are other safe and effective medications for nausea and vomiting during pregnancy, including:

• Vitamin B6 (Pyridoxine)

• Doxylamine (Unisom), often given with Pyridoxine

• Antihistamines such as meclizine (Antivert), diphenhydramine (Benadryl), or dimenhydrinate (Dramamine)

• Ondansetron (Zofran)

Can using marijuana while pregnant cause a miscarriage? 

We don’t have human studies that show that marijuana use increases risk of miscarriage. However, animal studies suggest there may be an increased link for miscarriage if used early in the pregnancy.

Can marijuana use in pregnancy cause underweight babies? 

Yes. Studies have shown that marijuana use during pregnancy can lead to a 50% increased chance of low birth weight. It is likely that more regular and long-term use of marijuana increases this risk.

Can marijuana use affect cognitive development?

Yes. Studies show that marijuana use can affect the brain development of babies and lead to developmental and mental health problems such as ADHD, as well as behavioral problems later in life. 

What if my partner uses marijuana?

Marijuana use isn’t only problematic for those who are pregnant or breastfeeding. Partners play a role as well. Early studies suggest that male partners of women who use marijuana at least weekly have an increased risk of a miscarriage.

And if a partner or household member smokes marijuana, there are additional risks: Second-hand marijuana smoke can lead to multiple health problems for children and can have negative effects on their brain development.

What about marijuana use while breastfeeding? 

If you’re breastfeeding, you’re advised to not use marijuana. Studies suggest that marijuana use while breastfeeding could lead to delays in motor development at age 1. And while studies are limited in this area, researchers suspect marijuana exposure in breastfed babies could impact brain development.

Will THC get into breast milk?

Yes. Marijuana goes through breast milk. In fact, it can be detected in breast milk for up to 6 weeks. We also know that second-hand marijuana smoke can negatively impact children’s health and should be avoided.

Since marijuana products are not regulated by the Food and Drug Administration (FDA), there is the additional concern of contamination of these products with heavy metals, pesticides, or other chemicals that could harm your baby.

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Written by:

Christina Palmer, MD

Christina Palmer, MD, is a board-certified family physician with a special interest in chronic care management, women’s health, mental health, and preventive care. She has over 10 years of experience in primary care research, innovation, and practice.

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