Smoking pot while pregnant — will it harm the baby later on?

Dear Alice,

What happens if you smoke weed while you are pregnant? Will the baby have problems in the future?

Dear Reader,

Great question! This is something about which some soon-to-be parents are very curious. With a number of states in the US legalizing marijuana use, some researchers anticipate increases in the percentage of parents who use it while pregnant. Although no clear-cut deformity or syndrome is currently known to occur due to marijuana use during pregnancy (whereas alcohol use is associated with fetal alcohol syndrome), there are other possible health risks. With this in mind, it’s best that parents avoid using marijuana while pregnant or nursing.

Some of the main health concerns of interest are:

  • Oxygen deprivation: In general, smoking anything during pregnancy deprives the fetus of oxygen. A lack of oxygen interferes with the fetus’s blood supply, and they may be born smaller in both weight and height. Smaller babies have a higher risk of other problems after birth, such as infections, severe jaundice, difficulty feeding, breathing problems, low blood sugar, difficulty regulating temperature, bleeding into the brain, and problems with vision.
  • Tetrahydrocannabinol (THC) transmission: THC, the main active ingredient in marijuana, has been found to be as much as eight times higher in breast milk than in the parent’s bloodstream. Babies exposed to marijuana during pregnancy or while nursing may sometimes seem jittery and difficult to comfort. They may have some delay in the development of their motor skills, although studies have concluded that this delay may not be permanent.
  • Preterm birth: Marijuana use during pregnancy has been associated with preterm birth (birth occurring before 37 weeks of pregnancy) and stillbirth.
  • Laced marijuana: It's possible that marijuana may be mixed (sometimes referred to as laced) with other drugs or substances without the user’s knowledge. As a result, the fetus may be unintentionally exposed to other potentially harmful substances.

Marijuana is the most commonly reported substance used during pregnancy. That being said, many studies have trouble parsing out the effects of marijuana specifically, as many of those who reported using marijuana also reported using alcohol and tobacco during the same time period. Due to known links between alcohol and tobacco use and serious birth defects, medical professionals suggest that those who use these substances stop use while pregnant. During the nursing period, it's commonly recommended to drink only modest amounts of alcohol (if they choose to drink), delay breastfeeding for two to three hours after drinking alcohol, and avoid exposing the baby to secondhand smoke. For those who have used marijuana for therapeutic purposes, it may be helpful to speak with a health care provider about alternative forms of treatment for the duration of the pregnancy and breastfeeding.

It can be noted that much of the research on the effects of prenatal exposure to marijuana has been complicated and inconclusive. This is mainly because it’s difficult to isolate the effects of marijuana from other possible factors such as alcohol, other drug use, and parental health. However, despite these challenges, researchers have identified some concerns regarding marijuana use for those who are pregnant. All in all, the safest choice for pregnant parents and their babies is to avoid using recreational drugs, including marijuana, while pregnant or nursing. While it may be challenging to adjust one’s lifestyle while pregnant or nursing, taking a break from using drugs and alcohol helps set babies up for long, healthy lives.

If you're interested in becoming pregnant, you may find it helpful to speak with your health care provider about any health concerns or behaviors that may affect the pregnancy. If you're already pregnant, speaking with a health care provider can help you monitor the pregnancy and recommend how to keep you and the fetus healthy. For even more information, check out Marijuana Use During Pregnancy and Lactation from The American College of Obstetricians and Gynecologists.

Last updated May 11, 2018
Originally published Sep 06, 2002

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