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Danger of Marijuana Use While Pregnant… Or a Smear Campaign?

Does marijuana have a bad affect on pregnant women?
Written by Sarah Friedman

Recent study on marijuana use by pregnant women, draws negative conclusions without considering important factors like smoking

Smear campaigns are all around, and can usually be identified by their unbacked arguments, and lacking information. Such is the case with the study I’ll go over today on whether marijuana causes issues if used while pregnant. What does the study say, what is it leaving out, and what does this mean? You can form your own opinion in the end.

This article is the specific opinion of the writer in response to a published research report on the dangers of marijuana use while pregnant.

The study on the dangers of marijuana use for pregnant women

The study in question was recently published, and is called The impact of timing of in utero marijuana exposure on fetal growth. According to the study investigators, the purpose of the study was “To examine whether timing of in utero marijuana exposure independently and negatively impacts fetal growth, and if these effects are global or specific to certain growth parameters.”

The study setup consisted of two groups, one with marijuana users (‘Marijuana Only’) and one for non-users (‘Control Group’) in which the non-use was verified with a drug test. The data collection for the study was not direct, with all data coming from investigation of electronic medical records. This means the investigators had no ability to set their own parameters or controls for collection. All the participants were pregnant and receiving care at an academic hospital (unnamed). All participants were 17 and above, and had a single birth within the time frame of 2016-2020.

The women chosen had their medical information reviewed to look for information on substance use during their pregnancies. Nothing was asked directly of the women by study investigators. Women were not included if they didn’t provide substance use information, or if they had documented alcohol issues or issues with other hard drugs.

Marijuana or smoke more likely to cause issues when pregnant
Marijuana or smoke more likely to cause issues when pregnant

In order to get classified into the ‘Marijuana Only’ group, an expectant mother said they used marijuana during pregnancy, or had a positive marijuana test during pregnancy. Most women had a urine drug test upon beginning care. 82% had a drug screen in the interim period, 90% had one at delivery, and 78% had newborn cord blood tested.

The women in the ‘Marijuana Only’ group denied use of other substances then marijuana, including tobacco, electronic cigarettes, alcohol, and other illicit drugs. All testing during labor was negative for anything except marijuana. None of the chosen participants had current prescriptions for opioids, benzodiazepines, or barbiturates. The only difference between the ‘Marijuana Only’ group and the ‘Control Group’, was the presence of marijuana. 109 women ended up in the ‘Marijuana Only’ group, and 171 in the ‘Control Group.’

Main findings of the study

According to the study investigators, there was a significant decrease in the weight of newborn babies when the mother used marijuana in just the first trimester, or during the whole pregnancy. They also found significant decreases in the circumference of the babies’ heads when the babies were exposed to marijuana in the first or second trimester, or throughout the pregnancy. They did not find any difference between the user group and the non-user group in terms of the length of the babies.

According to the researchers, “Timing of marijuana exposure appears to play a key role in specific fetal growth deficits, with exposure throughout gestation most detrimental.” They go on to say that even just using in the first trimester can affect birth weight. However, they do stipulate, that the lack of information on the timing of use, and amount used, make it difficult to judge this. Some women, for example, only smoked marijuana when first pregnant, and no questions were asked about amount or frequency of use.

They also drew other conclusions, like that mothers in the ‘Marijuana Only’ group were generally younger, more often single, usually not beyond a high-school education, and more often than the ‘Control Group’ women, covered by Medicaid. They also pointed out that the ‘Marijuana Only’ group gained more weight than the ‘Control Group’ while pregnant.

In the discussion, they sum up by saying “The results of this study support the hypothesis that marijuana use throughout pregnancy, compared to use only early in pregnancy, has the greatest impact on fetal growth, with both newborn weight and head circumference impacted.”

Smoking and low birth weight
Smoking and low birth weight

Were the women asked if they smoked the weed?

The investigators did say they had some limitations in the study. They list things such as the limited sample size, possibly not knowing if a woman was using some other drug within the overall pregnancy time period; human error; the ability to generalize to the population at large; and the lack of information on the amounts of marijuana used, and timing of use, by different participants. This last point is already a pretty big thing to leave out. Smoking a couple joints during a pregnancy, and smoking five times a day, are wildly different.

But the bigger omission is the deadlier one for a piece of research like this. Something that the researchers failed to mention, whether they had data on it or not. In fact, its the most important factor to consider. And it was absolutely, 100% disregarded as if not important. Not even mentioned once. The researchers never considered how the marijuana was consumed, and most importantly, if it was smoked.

All of these things the investigators relate in the study, are known side-effects of smoking when pregnant. And I don’t mean cigarettes specifically. Smoking is the act of lighting something on fire and breathing it in. And though we’re often taught to think of that solely in the context of cigarettes, this is not true at all.

Smoke inhalation is the breathing in of any smoke, whether from a house fire, a wildfire, plastic burning, or if a person smokes something like cigarettes or weed. All of this is smoke inhalation, and all smoke inhalation is detrimental. Although having said that, breathing in burning plastic will likely land you in emergency care before smoking a cigarette; so there are degrees.

If all – or the majority – of the women were smoking it (and this is highly likely based on the dates and that smoking is still the most popular form of use), then these results are literally 100% meaningless. This is an entire study that backs up the damage of smoke on a fetus, not of marijuana use. And while this isn’t to say that marijuana can’t have a bad effect for a pregnant women, it just means this study did nothing to back up that idea.

Smoke inhalation damage to fetuses

The reality of life, however unfortunate it is, is that the powers that be think you’re dumb. They think you’re so dumb, that they dumb down information either because they think you can’t understand it, or want you to think in a specific way. And because of this, if you look up ‘smoke damage to fetus,’ nearly all results will be geared toward smoking cigarettes. Here, however, is a study talking about general smoke damage to fetuses.

Woman smoking while pregnant
Woman smoking while pregnant

In reality, any information on smoke inhalation makes it clear this is not specifically about cigarettes. So once we apply the idea of smoke inhalation to all smoking, smoking marijuana is included as well. In this context, smoking anything should be accounted for; and it’s a massive, horrible failure for researchers to release something like this, with no mention of that.

For anyone confused on the matter, I suggest acquainting yourself with what ‘smoke inhalation’ means. This is not a controversial definition. According to WedMD, “Smoke inhalation occurs when you breathe in the products of combustion during a fire.”

Then ask yourself, what smoking is. Does it involve lighting something on fire and inhaling? Sure does! Its a fire from which smoke is repeatedly going directly into your lungs. And that’s the byproducts of combustion, directly inhaled, over and over. The exact definition of smoke inhalation. What’s one of the biggest issues with the main source of smoke inhalation while pregnant (cigarettes)? Low birth weight. In fact, here’s a study talking about the low birth weight that comes from exposure to wildfires in Brazil! It’s not just about cigarettes, guys. Smoke has been shown repeatedly to have this effect.

This study represents a concerning trend in the world of research, wherein researchers are so desperate to put something out, that they create links in information, and then hide what doesn’t go along with them. This is the second time I’ve seen this particular smear campaign of attaching marijuana to something negative, while not broaching the topic of smoking. In fact, in this example, the researchers were saying there was a link between marijuana and heart attacks, but they only used people who specifically smoked it, and didn’t once mention the issue of smoke inhalation as a possible cause.

As one last backing point to my argument, consider that the UK recently released news of a new program to get people to stop smoking by swapping cigarettes for vapes. That’s how much of a difference there is, even if that only refers to cigarettes. And what is one of their primary concerns in this? Getting pregnant women to switch to vaping first. How you ingest something is incredibly important, and its too bad that the researchers on this project didn’t understand this concept, or purposefully left it out (not sure which is worse).


I’m a writer, I don’t make laws or tell people what to do. However, my personal advice? If you’re pregnant, maybe stay away from any substances you don’t have to use. We don’t have an answer on everything, and sometimes the safest bet, is choosing the safest bet. Having said that, if you’re pregnant and trying to find answers about marijuana, best to find a better information source than this study.

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About the author

Sarah Friedman

I look stuff up and and write stuff down, in order to make sense of the world around. And I travel a lot too.