Why Does the Surgeon General Advise Pregnant Women to Avoid Marijuana?

Pregnant woman avoiding marijuana.

As one state after another legalizes the use of marijuana, it might be harder than ever before to learn the truth about marijuana use. Is it harmful? Is it safe? If you ask an advocate for the cannabis industry, you’ll hear about the positive side of cannabis use. But are they the right authority? And who should pregnant women listen to as they guard the health of their unborn children? Recently, the Surgeon General of the United States issued an advisory that provides authoritative guidance for pregnant and nursing women.

Here are some vitally important points from his advisory and from its citations.

  1. Marijuana is the most frequently used drug among pregnant women. Approximately seven percent of pregnant women consume marijuana.
  2. According to one survey, the number of pregnant woman using this drug more than doubled between 2002 and 2017.
  3. THC, the intoxicant most users consider desirable, passes through the placenta to the baby.
  4. This THC binds to the cannabinoid receptors in the brain of both the mother and the baby. These receptors are critical for brain development in the baby. Cannabinoid receptors are part of the endocannabinoid system, the development of which prepares a person for decision-making and influences their moods and ability to respond to stress.
  5. Use of marijuana during pregnancy is associated with higher levels of adverse outcomes, including lower birth weight. One study found that this risk increased among mothers who used cannabis as infrequently as once a week during pregnancy.
  6. Some studies have found that pregnant women who use marijuana have a greater risk of pre-term birth.

The Surgeon General also recommends this page of frequently-asked questions about pregnancy and marijuana use: FAQ from the American College of Obstetrics and Gynecology.

Even aside from the effect on the developing baby, marijuana use can have other undesirable effects:

  1. THC is found in breast milk for as long as six days after the mother’s last use.
  2. It’s even been shown that THC reduces the fertility of women.
  3. If a woman’s spouse uses marijuana at the time they conceive, the drug can affect a man’s sperm adversely, resulting in a greater risk of miscarriage.

It has become general knowledge that women should not use alcohol during pregnancy and indeed, many women stop drinking as soon as they know they are pregnant. With marijuana, it’s completely different.

It might seem hard to believe but there are many people who actually recommend marijuana use during pregnancy. There are also some women who were not marijuana users before they were pregnant but began using after they became pregnant.

Gravitating to Marijuana Use during Pregnancy

Woman in a marijuana store.
(Photo by Krysja/Shutterstock.com)

Who recommends marijuana use during pregnancy? The staff at marijuana dispensaries, for one. At a university in Colorado, researchers contacted 400 businesses that offered marijuana for medical use, recreational use or both. The researchers posed as pregnant women experiencing morning sickness. Would the dispensaries recommend the use of this drug by these women?

Sixty-nine percent of the dispensary staff recommended use of marijuana by this “pregnant” caller. Only 32% suggested that the woman speak to their doctor first. When prompted with a direct question, this percentage rose to 82%.

Women who have used marijuana during pregnancy also recommend it to other women. There are actually online forums specifically for women who smoke marijuana during pregnancy. I don’t want to promote those websites but you can find them with an internet search with terms like “pregnancy cannabis forum.” A quick look at these forums shows that many of these women smoke cannabis every day of their pregnancies and continue smoking as they breastfeed.

Questions that Need to Be Asked

There are some vitally important questions about marijuana use in pregnancy that I have never seen anyone ask or answer.

It is well known that THC is attracted to a person’s fat cells and it tends to remain in those cells even if a person stops using the drug. A 2009 study found that under certain conditions such as food deprivation or stress that this THC can be released back into the bloodstream, resulting in what the study calls “reintoxication.” In other words, measurable amounts of THC can be found in a person’s blood, even if they have not touched the drug for an extended period of time, when conditions are right to release the drug into the bloodstream.

So when a pregnant woman uses marijuana and she passes this drug on to her baby, that drug is just as likely to be stored in the baby’s fat cells as hers. So here’s what needs to be asked and answered:

  • What will the short-term and long-term effects of the presence of this drug in the baby’s body be?
  • How long will THC remain in the baby’s body?
  • Will that person be particularly attracted to marijuana when they encounter it at a later age?
  • When they try it, will the residual presence of this drug make marijuana more attractive or enticing?
  • Will that person be any more likely to become a habitual user?

We don’t know. I have heard of no scientists or doctors who have yet raised these points. But they are points each parent—especially a mother-to-be—should perhaps reflect on.

As with all drugs, the best way to bear a healthy child is to avoid drug abuse, eat a healthy diet and avoid toxins wherever possible.


Reviewed by Claire Pinelli, ICAADC, CCS, LADC, MCAP RAS


Karen Hadley

For more than a decade, Karen has been researching and writing about drug trafficking, drug abuse, addiction and recovery. She has also studied and written about policy issues related to drug treatment.