Strong public policy suggests that cannabis use during pregnancy is dangerous to your health, but what does the research say?
Some of my friends have babies and some of my friends smoke pot. Sometimes they do both — and not too long ago, a friend asked me if it was safe to smoke during pregnancy.
To answer this question, I needed to prepare and gather information, so I told her I would get back to her the next day. It took me much longer: with a quick search of the health sciences literature database, I found a bunch of studies on the topic — about 500 scientific articles on cannabis-related pregnancy. What was even more surprising was that these studies were spread in different directions — they didn't boil down to one unambiguous truth, and in fact many of them contradicted each other.
Then I discovered something even more startling: many states, including those where pot is legal, severely penalize Americans for cannabis use during pregnancy, often allowing courts and child welfare agencies to charge parents with child abuse or neglect.
Some of my friends have babies and some of my friends smoke pot. Sometimes they do both — and not too long ago, a friend asked me if it was safe to smoke during pregnancy.
To answer this question, I needed to prepare and gather information, so I told her I would get back to her the next day. It took me much longer: with a quick search of the health sciences literature database, I found a bunch of studies on the topic — about 500 scientific articles on cannabis-related pregnancy. What was even more surprising was that these studies were spread in different directions — they didn't boil down to one unambiguous truth, and in fact many of them contradicted each other.
Then I discovered something even more startling: many states, including those where pot is legal, severely penalize Americans for cannabis use during pregnancy, often allowing courts and child welfare agencies to charge parents with child abuse or neglect.
In addition, many states (not necessarily the same states) have policies requiring health care providers to report drug use by pregnant women at the time of diagnosis.
Cannabis is just one of many drugs for which such punitive policies exist: they also apply to a number of other substances, including cocaine, methamphetamine, and opioids. But cannabis is used by more pregnant women than any of these other drugs, especially as states increasingly legalize its sale and use.
Horror stories have emerged as shaky science intersects with legislation in a society eager to regulate women's bodies, especially those of pregnant women.
But the most damaging may be the broader impact of these policies: by making pregnancy providers the body of law, they create a climate of fear and mistrust between prenatal providers and patients.
These are the very places where pregnant women would ideally learn to minimize the harm that drug use can do to their pregnancy. However, both patients and providers have incentives to never mention it, and fear of being caught can lead patients to avoid medical care altogether.
Cannabis is just one of many drugs for which such punitive policies exist: they also apply to a number of other substances, including cocaine, methamphetamine, and opioids. But cannabis is used by more pregnant women than any of these other drugs, especially as states increasingly legalize its sale and use.
Horror stories have emerged as shaky science intersects with legislation in a society eager to regulate women's bodies, especially those of pregnant women.
But the most damaging may be the broader impact of these policies: by making pregnancy providers the body of law, they create a climate of fear and mistrust between prenatal providers and patients.
These are the very places where pregnant women would ideally learn to minimize the harm that drug use can do to their pregnancy. However, both patients and providers have incentives to never mention it, and fear of being caught can lead patients to avoid medical care altogether.
It is very difficult to prove the effects of cannabis on the human fetus
People use cannabis during pregnancy for a variety of reasons. Most of them are trying to cope with pregnancy symptoms, most commonly nausea and vomiting, which about 70% of pregnant women say is the reason for using cannabis. Other symptoms that people treat with this drug include anxiety, pain, headaches, cramps, sleep disturbances and poor appetite.
Cannabis use during pregnancy wouldn't be a problem if it didn't expose the growing fetus to a substance that could theoretically harm it. Unfortunately, it does.
During pregnancy, the fetus receives nutrients and oxygen from the parents' blood, but only after they are filtered through the placenta, a temporary organ that grows with the fetus inside the uterus (and leaves the uterus with the fetus during delivery).
When a pregnant woman uses marijuana, her fetus probably has 2.5 to 6 times less tetrahydrocannabinol (THC), the main psychoactive compound found in cannabis, in their bloodstream than they do.
In addition to THC, more than 100 different compounds in cannabis exert a range of effects through the endocannabinoid system, a set of neurotransmitters and their receptors scattered throughout the human and animal body, including (but not limited to) their brains. Within this system, cannabis compounds mimic natural neurotransmitters that are normally recognized by receptors.
People use cannabis during pregnancy for a variety of reasons. Most of them are trying to cope with pregnancy symptoms, most commonly nausea and vomiting, which about 70% of pregnant women say is the reason for using cannabis. Other symptoms that people treat with this drug include anxiety, pain, headaches, cramps, sleep disturbances and poor appetite.
Cannabis use during pregnancy wouldn't be a problem if it didn't expose the growing fetus to a substance that could theoretically harm it. Unfortunately, it does.
During pregnancy, the fetus receives nutrients and oxygen from the parents' blood, but only after they are filtered through the placenta, a temporary organ that grows with the fetus inside the uterus (and leaves the uterus with the fetus during delivery).
When a pregnant woman uses marijuana, her fetus probably has 2.5 to 6 times less tetrahydrocannabinol (THC), the main psychoactive compound found in cannabis, in their bloodstream than they do.
In addition to THC, more than 100 different compounds in cannabis exert a range of effects through the endocannabinoid system, a set of neurotransmitters and their receptors scattered throughout the human and animal body, including (but not limited to) their brains. Within this system, cannabis compounds mimic natural neurotransmitters that are normally recognized by receptors.
Scientists have found that in animals, the connectivity of this system develops differently in the brain of fetuses when they are exposed to cannabis intrauterine. In rats, these differences translate into behavioral differences in babies born to rat mothers exposed to cannabis: they are more anxious; they are less social; they do not remember, learn or pay attention in the same way as other rats; and they are potentially more prone to opioid addiction.
About 16 percent of Americans claim to smoke pot. The percentage who do so during pregnancy is lower, probably averaging about 7%. Among young, low-income urban pregnant women, the rate ranges from 15% to 28%. Pregnant people are about twice as likely to use cannabis in states where it is legal than in states where it is illegal (7% vs. 2.5%).
In a minority of cases — about a quarter in one study — pregnant cannabis smokers meet criteria for a substance use disorder, which suggest that use harms their function or their relationships in some way.
But «plausibility» is not proof — and for decades scientists have been studying children exposed to cannabis in utero to try to understand what's really going on.
About 16 percent of Americans claim to smoke pot. The percentage who do so during pregnancy is lower, probably averaging about 7%. Among young, low-income urban pregnant women, the rate ranges from 15% to 28%. Pregnant people are about twice as likely to use cannabis in states where it is legal than in states where it is illegal (7% vs. 2.5%).
In a minority of cases — about a quarter in one study — pregnant cannabis smokers meet criteria for a substance use disorder, which suggest that use harms their function or their relationships in some way.
But «plausibility» is not proof — and for decades scientists have been studying children exposed to cannabis in utero to try to understand what's really going on.
This is not the best way to get an answer to the scientific question of what effect a particular drug has on pregnancy. In a world without bioethics, researchers asking such questions could conduct a study in which pregnant women would be randomized to take the drug or not, and then compare the results in babies born to each group. But because there is reasonable suspicion that cannabis can cause harm, and because it's illegal at the federal level, researchers can't conduct human studies.
Instead, scientists are doing observational studies in which they literally observe what happens to babies born to people who choose to use cannabis. They can be informative, but they're not perfect.
People who use cannabis during pregnancy can be significantly different from people who don't. It's hard to know from these studies whether weed or a related factor — mental health, anxiety, demographics — is the cause of any differences between their children.
So what does the research tell us?
Most of the data on the effects of cannabis on the fetus during pregnancy come from three large observational studies that followed children born to mothers between 1982 and 2006.
Children born to cannabis-using mothers had differences that changed with age: sleep and decreased attention; 6-year-olds showed decreased attention span, increased hyperactivity and impulsivity, and decreased concentration; pre-adolescent and adolescent children had worse concentration and verbal reasoning, more severe depression, and higher rates of delinquency.
Since then, many other smaller studies have been conducted, but none have avoided the problems associated with observational studies. In a review of relevant 2020 studies published since the mid-1980s, the authors cited many of these studies as having weak methodology. In particular, many researchers failed to compare the outcomes they were measuring to any standard that took into account parents' age and education level.
That is: what if the children of those who used cannabis during pregnancy were born to parents with lower levels of education, which might explain some of the differences?
Instead, scientists are doing observational studies in which they literally observe what happens to babies born to people who choose to use cannabis. They can be informative, but they're not perfect.
People who use cannabis during pregnancy can be significantly different from people who don't. It's hard to know from these studies whether weed or a related factor — mental health, anxiety, demographics — is the cause of any differences between their children.
So what does the research tell us?
Most of the data on the effects of cannabis on the fetus during pregnancy come from three large observational studies that followed children born to mothers between 1982 and 2006.
Children born to cannabis-using mothers had differences that changed with age: sleep and decreased attention; 6-year-olds showed decreased attention span, increased hyperactivity and impulsivity, and decreased concentration; pre-adolescent and adolescent children had worse concentration and verbal reasoning, more severe depression, and higher rates of delinquency.
Since then, many other smaller studies have been conducted, but none have avoided the problems associated with observational studies. In a review of relevant 2020 studies published since the mid-1980s, the authors cited many of these studies as having weak methodology. In particular, many researchers failed to compare the outcomes they were measuring to any standard that took into account parents' age and education level.
That is: what if the children of those who used cannabis during pregnancy were born to parents with lower levels of education, which might explain some of the differences?
The authors of the review concluded that, in general, «prenatal exposure to cannabis had little effect on offspring cognitive function». Moreover, they noted that even when abnormalities were identified, almost all of them remained within the normal range.
Problems with the design of many studies stem from the biases that many researchers bring to the table. If you look at studies of pharmaceuticals, you will see that they start from innocent until proven guilty, whereas banned substances are considered guilty until proven innocent. In other words, «It's like we're programmed to think there will be harm».
Cannabis is even safer than some alternatives
Despite imperfect data, the risk of fetal harm from prenatal cannabis use is high enough to recommend against recreational use alone. But many don't seek only to get high.
For three years, Shonitria Anthony has been hosting the podcast and online community Blunt Blowin' Mama, which aims to normalize the behavior of pot-smoking moms. In that time, she says, not a single mom has told her that she smokes during pregnancy just to get high. She says they mostly try to use the smallest amount they can get away with while managing their symptoms, such as nausea and pain.
But here's where things get tricky.
The American College of Obstetricians and Gynecologists recommends that doctors advise pregnant women to avoid using cannabis in favor of an alternative. But in many cases, doctors simply say — «Cannabis is dangerous, so don't use it».
Problems with the design of many studies stem from the biases that many researchers bring to the table. If you look at studies of pharmaceuticals, you will see that they start from innocent until proven guilty, whereas banned substances are considered guilty until proven innocent. In other words, «It's like we're programmed to think there will be harm».
Cannabis is even safer than some alternatives
Despite imperfect data, the risk of fetal harm from prenatal cannabis use is high enough to recommend against recreational use alone. But many don't seek only to get high.
For three years, Shonitria Anthony has been hosting the podcast and online community Blunt Blowin' Mama, which aims to normalize the behavior of pot-smoking moms. In that time, she says, not a single mom has told her that she smokes during pregnancy just to get high. She says they mostly try to use the smallest amount they can get away with while managing their symptoms, such as nausea and pain.
But here's where things get tricky.
The American College of Obstetricians and Gynecologists recommends that doctors advise pregnant women to avoid using cannabis in favor of an alternative. But in many cases, doctors simply say — «Cannabis is dangerous, so don't use it».
Yes, cannabis may come with some risks. But it may well be that these risks are not as serious as the alternatives.
Let's say a pregnant woman is using cannabis as a nausea medication. If a doctor tells them to stop using it, the alternative is that they may just get nauseous and not be able to eat. This comes with its own risks; the growing fetus needs nutrition.
Or let's say they're using cannabis to manage pain. If they're using it for pain management, and their alternative is to use opioids, which cause a whole host of negative effects on the fetus, then we need to rethink the conversation.
In these situations, we have to ask the question: what will cause less harm? The answer may be cannabis. (Ideally, a pregnant woman would not consider using prescription opioids; however, nearly 7% of pregnant women do, and one in five of them abuse drugs)
Legal pharmaceutical drugs are sometimes an option for treating pregnancy-related symptoms. But there are risks and unknowns here, too. The vast majority of medications have not been evaluated for their safety during pregnancy. Therefore, there is little choice of known safe options.
It could be argued that even legal drugs, whose safety has been verified, have been much less studied over the years than cannabis. There is a larger evidence base for neurocognitive development as a result of cannabis exposure than there is for the drugs we prescribe.
For patients who trust the products with the greatest evidence base, cannabis may seem like a much safer choice than some pharmaceuticals.
Let's say a pregnant woman is using cannabis as a nausea medication. If a doctor tells them to stop using it, the alternative is that they may just get nauseous and not be able to eat. This comes with its own risks; the growing fetus needs nutrition.
Or let's say they're using cannabis to manage pain. If they're using it for pain management, and their alternative is to use opioids, which cause a whole host of negative effects on the fetus, then we need to rethink the conversation.
In these situations, we have to ask the question: what will cause less harm? The answer may be cannabis. (Ideally, a pregnant woman would not consider using prescription opioids; however, nearly 7% of pregnant women do, and one in five of them abuse drugs)
Legal pharmaceutical drugs are sometimes an option for treating pregnancy-related symptoms. But there are risks and unknowns here, too. The vast majority of medications have not been evaluated for their safety during pregnancy. Therefore, there is little choice of known safe options.
It could be argued that even legal drugs, whose safety has been verified, have been much less studied over the years than cannabis. There is a larger evidence base for neurocognitive development as a result of cannabis exposure than there is for the drugs we prescribe.
For patients who trust the products with the greatest evidence base, cannabis may seem like a much safer choice than some pharmaceuticals.
While the science linking prenatal marijuana use to pregnancy outcomes is far from complete, laws in many U.S. states punish people quite severely for using the drug during pregnancy.
About half of the states consider any substance use during pregnancy to be equivalent to child abuse, including marijuana, regardless of whether recreational or medical use is legal in that state.
Three also consider it grounds for involuntary hospitalization in a drug treatment center, and three consider it grounds for criminal prosecution —meaning that people found using drugs during pregnancy could end up in jail.
Since the policy first entered the legislative lexicon in the mid-1970s, the penalties it imposed have fallen disproportionately on black people.
There are also extremely confusing policies regarding testing and reporting prenatal drug use. A number of state policies require health care providers to test and/or report pregnant people or newborns for drug use or exposure when they suspect it.
About half of the states consider any substance use during pregnancy to be equivalent to child abuse, including marijuana, regardless of whether recreational or medical use is legal in that state.
Three also consider it grounds for involuntary hospitalization in a drug treatment center, and three consider it grounds for criminal prosecution —meaning that people found using drugs during pregnancy could end up in jail.
Since the policy first entered the legislative lexicon in the mid-1970s, the penalties it imposed have fallen disproportionately on black people.
There are also extremely confusing policies regarding testing and reporting prenatal drug use. A number of state policies require health care providers to test and/or report pregnant people or newborns for drug use or exposure when they suspect it.
Hospitals can also make their own testing and reporting protocols — and while they must follow state laws about what to do with the information they receive, they can report parental drug use to child welfare authorities, even if the state does not require it. And while parents can't be drug tested without their consent, newborns can.
If a child tests positive for a drug — and the child's feces, urine and blood can test positive for cannabis — state policies related to the substance apply to the parent.
Even in states that don't have laws specifically against drug use during pregnancy, prosecutors sometimes bring cases against people who use drugs during pregnancy.
All of these punitive policies create an incredibly confusing environment for both patients and providers. It forces providers to simply avoid asking or talking about cannabis use during clinic encounters.
This confusion leads to several realities that end up being bad for both children and parents. First, it means that medical professionals are so confused about what they need to do if they find out a pregnant patient is using cannabis, so they simply avoid the topic. Many practitioners don't actually confront the issue of cannabis directly with patients and simply try not to talk about it.
But what is particularly disturbing is the impact of these policies on pregnant patients. Instead of getting pregnant women to stop using drugs, punitive drug policies make them avoid seeking prenatal care, probably because this is the setting in which they would be identified as drug users.
If a child tests positive for a drug — and the child's feces, urine and blood can test positive for cannabis — state policies related to the substance apply to the parent.
Even in states that don't have laws specifically against drug use during pregnancy, prosecutors sometimes bring cases against people who use drugs during pregnancy.
All of these punitive policies create an incredibly confusing environment for both patients and providers. It forces providers to simply avoid asking or talking about cannabis use during clinic encounters.
This confusion leads to several realities that end up being bad for both children and parents. First, it means that medical professionals are so confused about what they need to do if they find out a pregnant patient is using cannabis, so they simply avoid the topic. Many practitioners don't actually confront the issue of cannabis directly with patients and simply try not to talk about it.
But what is particularly disturbing is the impact of these policies on pregnant patients. Instead of getting pregnant women to stop using drugs, punitive drug policies make them avoid seeking prenatal care, probably because this is the setting in which they would be identified as drug users.
When people worry that they will lose their children if they go to the doctor while pregnant and using drugs, or [if] their primary care physician finds out they are using drugs, they will avoid medical care. This limits the ability to provide them not only with support to reduce their substance use, but also to link them to food, housing, and other medical care.
Unlike the effects of cannabis use, the results of inadequate prenatal care are unambiguously negative: the risk of low birth weight and infant mortality is several times higher in pregnancies that do not receive prenatal care, and the harm to both baby and mother from preventable Causes such as diabetes and pre-eclampsia can be reduced if care is initiated early in pregnancy.
In states with punitive prenatal substance use policies, more pregnant women overdose on opioids, fewer receive treatment for substance use disorders, and more babies are born with opioid and other complications such as prematurity and low birth weight.
What's gonna happen next?
The United States stands out among countries when it comes to penalizing drug use during pregnancy, and the negative consequences of its punitive approach disproportionately affect racial and ethnic minorities, particularly indigenous and black populations.
Moreover, while many laws penalize pregnant women for fetal drug exposure, there are no similar laws relating to tobacco — despite a much higher level of evidence linking tobacco use during pregnancy to lung problems and congenital abnormalities in newborns.
Unlike the effects of cannabis use, the results of inadequate prenatal care are unambiguously negative: the risk of low birth weight and infant mortality is several times higher in pregnancies that do not receive prenatal care, and the harm to both baby and mother from preventable Causes such as diabetes and pre-eclampsia can be reduced if care is initiated early in pregnancy.
In states with punitive prenatal substance use policies, more pregnant women overdose on opioids, fewer receive treatment for substance use disorders, and more babies are born with opioid and other complications such as prematurity and low birth weight.
What's gonna happen next?
The United States stands out among countries when it comes to penalizing drug use during pregnancy, and the negative consequences of its punitive approach disproportionately affect racial and ethnic minorities, particularly indigenous and black populations.
Moreover, while many laws penalize pregnant women for fetal drug exposure, there are no similar laws relating to tobacco — despite a much higher level of evidence linking tobacco use during pregnancy to lung problems and congenital abnormalities in newborns.
All of this suggests that these policies represent a long shadow of the country's drug-saturated history. Nixon's War on Drugs did force Americans to look at drug use as a moral failing and a legal problem rather than a medical problem.
Moral panic has motivated many drug and pregnancy policies in the US — and enough time has passed since then for us to learn from the events that followed. A key example is the 1990s nationwide excitement about drug-addicted children — a supposed epidemic of children born with disabilities due to in utero exposure to a certain type of cocaine.
Although prenatal exposure to crack cocaine was eventually found to have had little or no developmental impact, the separation of children from their mothers because of positive drug tests caused immeasurable harm to children and parents and disproportionately traumatized black families.
But overall, the moral panic around cannabis in the US is subsiding. It is more acceptable in many aspects of life and, increasingly, legal. Why is pregnancy insulated from the normalization and acceptance of the drug in many other parts of American society?
At this point, the policy is not motivated by science, nor is it motivated by public health. This seems uncomfortably familiar: many policies about reproductive health and the decisions people make during pregnancy have nothing to do with well-being. They reason only about control. This needs to change.
Moral panic has motivated many drug and pregnancy policies in the US — and enough time has passed since then for us to learn from the events that followed. A key example is the 1990s nationwide excitement about drug-addicted children — a supposed epidemic of children born with disabilities due to in utero exposure to a certain type of cocaine.
Although prenatal exposure to crack cocaine was eventually found to have had little or no developmental impact, the separation of children from their mothers because of positive drug tests caused immeasurable harm to children and parents and disproportionately traumatized black families.
But overall, the moral panic around cannabis in the US is subsiding. It is more acceptable in many aspects of life and, increasingly, legal. Why is pregnancy insulated from the normalization and acceptance of the drug in many other parts of American society?
At this point, the policy is not motivated by science, nor is it motivated by public health. This seems uncomfortably familiar: many policies about reproductive health and the decisions people make during pregnancy have nothing to do with well-being. They reason only about control. This needs to change.