Does Cannabis Harm Unborn Babies?

Health Anna Wilcox 5/2/2018
question of pregnant lady
Consuming cannabis while pregnant? Read this article first.

It’s in our nature to seek concrete, clear answers. Yet, when it comes to the question of whether or not it’s safe to consume cannabis during pregnancy, clear answers are few and far between.

The impacts of cannabis consumption are drastically understudied, which means that the information available is based on poor-quality research that makes it difficult to determine what impacts the herb might have.

However, regardless of unknown side effects, more women than ever are consuming cannabis during pregnancy.

In fact, from 2009 to 2016, research found that the number of women who reported consuming the herb while pregnant jumped from 4.2 to 7.1 percent.

Whether this is because more women are coming clean about consuming the herb or whether or not more mothers are actually consuming the herb, it’s difficult to say.

Yet, this statistic raises concerns among many health professionals. The overall effects of cannabis on an unborn baby are unknown, so no medical professionals can make any sound judgments on the matter.

What is known is that the herb works by engaging in a chemical network in the body that is important for the development of the brain and nervous system.

However, no one knows for sure what happens to a baby’s nervous system when it is exposed to high levels of cannabis compounds.

For this reason, most health professionals encourage pregnant women to avoid cannabis. But, what do we know about cannabis during pregnancy? What are the biggest concerns for partaking in the herb?

This guide is intended to highlight recent research on cannabis use during pregnancy, the good and the bad. Unfortunately, this guide will not provide a definitive answer on whether or not cannabis harms unborn babies.

Why? There is simply not an answer at this time. However, mothers are encouraged to talk to medical professionals and seek out as much information as possible before making the decision to partake.

The trouble with research on cannabis and pregnancy

pregnancy sign
We only have a few major studies in this area.

It is unethical to give pregnant women cannabis to see whether or not the herb causes significant damage on a child once it is born.

Therefore, there is no research available that gives a conclusive answer as to whether or not prenatal cannabis use harms unborn babies.

However, the lack of consistent and definitive research on this topic gives reason to be cautious and seek out more information before partaking in the herb while pregnant.

When looking for quality research, it’s always important to prioritize large-scale studies. Right now, much of the significant research on the impact of cannabis consumption during pregnancy stems from only three major studies.  

The first major study was based on data from the Maternal Health Practices and Child Development Study (MHPCD), which followed a group of children from low-income families.

The children had been exposed to cannabis in the womb and researchers reported on the children after they were born, at six years of age, and at 10.

The second oft-cited study is the Ottawa Prenatal Prospective Study (OPPS) which followed a group of mostly middle-class white women through their pregnancies.

Children were observed at ages one, three, and between the ages of nine and 12.

Finally, the third study was conducted in Jamaica by Dr. Melanie Dreher. This study followed 59 women through pregnancy and collected data on their children to five years of age.

About half of the mothers consumed cannabis during pregnancy. After age 5, this long-term study lost funding from the National Institutes on Drug Abuse (NIDA).

Unfortunately, none of these studies are very recent. The MHPDC began in 1982. The OPPS study began in 1978. The Jamaican study was also conducted in the 1980s.

While this research is longitudinal, meaning that it follows participants over long periods of time, much of today’s caution about prenatal cannabis consumption comes from research that is now decades old.

When it comes to breastfeeding, the research on cannabis is even worse. Most research was conducted over two decades ago.

That research is still being included as central sources of data in more recent reviews.

Does cannabis harm unborn babies?

So, based on this old research and a handful of new reviews, what sort of side effects can we expect from consuming cannabis while pregnant?

Does cannabis actually harm unborn babies? Based on this evidence, here are a few things research has taught us about the plant:

1. Cannabis is like caffeine

coffee with cannabis
Caffeine: the most popular drug ever?

While it’s not often described this way, caffeine is the most popular psychoactive drug in the world. In fact, an estimated 85 percent of the U.S. population consumes a caffeinated beverage at least once per day.

There’s a reason why doctors recommend limiting caffeine intake to 200 milligrams or less during pregnancy.

Developing babies do not have the enzymes needed to deactivate and detox the caffeine, meaning that excess amounts of caffeine metabolites can build up in a fetus’ brain.

For cannabis, an estimated 10 to 30 percent of the THC consumed by the mother crosses the placenta.

Unfortunately, no one really knows where psychoactive THC goes in a developing fetus and what impact it might have.

Yet, like caffeine, studies have shown that exposing an unborn baby to cannabis may pose an increased risk for decreased growth, low weight for gestational age, and low weight at birth.

While these risks are important to consider, it’s also important to acknowledge that these potential risks have not been consistent across all studies.

In Dreher’s Jamaican study, researchers found no difference between babies born to cannabis-consuming mothers and those who were not three days after birth and at 30 days.

Even more interesting, Dreher’s team found that babies exposed to cannabis in the womb were considered more enjoyable to work with and showed signs of superior health, including better nervous system functioning and improved alertness.

In fact, a 2016 review of scientific literature found no correlation between cannabis and negative birth outcomes.

However, the meta-analysis did find that combining cannabis and tobacco was associated with higher risks of low birth weight and decreased growth.

Similarly, an old 1997 review conducted in Australia analyzed 34,483 women hints that its the amount of cannabis consumed during pregnancy that may impact outcomes on the child, not the plant itself.

The research found that cannabis consumption once per week was associated with an increase in birth weight, contrasting previous studies. The OPPS and MHPCD studies also found an association between prenatal cannabis consumption and higher birth weight.

Yet, mothers who consumed multiple times a week were more likely to see a decrease in birth weight.

The study authors ultimately concluded, “Cannabis is unlikely to contribute to low birth weight when used in the amount typically taken by a pregnant woman.”

While not conclusive in the slightest, this suggests that perhaps someday in the future, safe limits for cannabis will be established. Though, not enough research is available to support this hypothesis.

2. THC is absorbed into a baby’s bloodstream and is passed along in breastmilk

mother breastfeeding new born child
Breastfeeding mothers also need to do their homework on cannabis.

One of the major arguments for using caution with cannabis during pregnancy is because the active compound in the plant, THC, can be absorbed into the bloodstream and is passed along to the fetus.

After a baby is born, THC and other cannabis compounds can also be passed along to the child via breastmilk.

It's this exposure to THC and other cannabinoids that have health professionals concerned.

Cannabis compounds just so happen to engage with one of the largest neurotransmitter receptors in the human body.

That neurotransmitter system is called the endocannabinoid system and it plays an important role in the development of the brain and nervous system.

Most recently, research in rodent models has found that both excesses and deficiencies in endocannabinoids can cause birth and brain complications in mice.

Endocannabinoids are neurotransmitter molecules similar to cannabis that the body produces naturally.

For example, the research from Dr. Sudhansu Dey at the University of Cincinnati has found that fetal mice exposed to imbalances of endocannabinoids in the womb were more likely to develop seizure disorders after birth.

Yet, this research is experimental and Dr. Dey is quick to explain that there is no way of knowing whether or not cannabis exposure can cause the same effects, or whether or not endocannabinoids have this same effect in humans.

What is clear from Dr. Dey’s research, however, is that having just the right balance of endocannabinoids is helpful for creating positive birth outcomes.

3. Memory, attention, and learning later in life

Even if cannabis is not associated with negative effects at birth, many public health and medical officials are still wary about the long term.

Due to the fact that endocannabinoids are vital to brain development, researchers are concerned that exposure to high doses of cannabis compounds may have long-term impacts on a baby’s brain.

While the Jamaica study found “absolutely no difference” between babies exposed to cannabis in the womb and those who were not, both the MHPCD and the OPPS study found correlations between prenatal cannabis consumption and hyperactivity, impulsivity, and inattention by the ages of 10 to 12.

Yet, in Dr. Dreher’s study, it was school attendance and home environment that had an impact on learning and behavior, not cannabis consumption.

In a lecture, she explains:

The child who attends basic school regularly is provided with a variety of stimulating experiences at home, who is encouraged to show mature behavior, has a profoundly better chance of performing at a higher level.

4. Infection

infection around unborn child
Contaminated cannabis could potentially harm a fetus.

One potential problem not oft discussed when it comes to cannabis and pregnancy is not caused by the cannabis itself.

Rather, it's important to avoid consuming moldy cannabis. Unfortunately, without a microscope, finding mold on bud can be difficult.

This potentially increases the risk of illness or infection. Prenatal infection has been linked to numerous negative health outcomes in infants, including schizophrenia.

So, while the cannabis itself may not be the problem, a lack of oversite or laboratory testing of cannabis products may very well be.

5. Pesticide exposure

ecig and pregnancy
Pesticides are huge issue in cannabis and an even bigger issue for developing fetuses.

For those who choose to consume cannabis during pregnancy, pesticide exposure may also be problematic.

Non-organic cannabis increases the risk of exposure to unsafe levels of pesticides, and finding safe cannabis may be troublesome for those in non-legal states.

In fact, a 2015 paper published in the Journal of Toxicological Sciences found that 80 percent of 57 random cannabis concentrate samples tested positive for unsafe levels of pesticide.

These concentrates are common additives to vape pens, which women may use to ease morning sickness, nausea, or pain associated with pregnancy.

Like cannabis compounds, pesticide residues, pollutants, and heavy metals can be passed along to a baby via breast milk.

While research in Australia has shown that pesticide levels in breast milk have decreased over the past several years, scientists remain concerned that levels of pesticides and other pollutants in breast milk can interfere with an infant’s developing hormonal system.

Also similar to some of the results from cannabis research, high levels of certain types of pesticides in breast milk was correlated with increased hyperactivity in children by five years of age.

With so many cannabis products not tested for residual pesticides, expecting mothers may be unintentionally exposing their babies to unsafe levels of the pollutants.

Education, not criminalization

As you can see, there are no simple answers when it comes to cannabis and pregnancy.

Research on the subject falls all over the board.  

In either case, no mother should face criminal consequences nor a visit from child services for the decision.

Above all else, consuming cannabis during pregnancy s a public health issue, not a criminal one.

Mothers who admit to consuming cannabis while pregnant – or in general – can face jail time and risk having their child taken away by social services.

This criminalization approach suggests that allowing a child to grow up away from its mother, potentially placed in foster care, and potentially unable to be nursed by its mother’s own breast milk causes less damage than prenatal THC exposure.

To be clear, when it comes to pregnancy, it is always recommended to follow the guidance and expertise of a trusted medical professional.  

Yet, there is no need to be alarmist or sensational about the effects of cannabis use during pregnancy.

While more research is sorely needed, some of the studies conducted have found some potential risks.

If mothers-to-be know what the possible outcomes are, they are better able to make informed decisions that best suit their individual needs.

Due to a sheer lack of high-quality and consistent information about prenatal cannabis consumption, any wise doctor or midwife would explain that the effects of the herb are unknown and that there seems to be a possibility of negative health outcomes.

With no safe consumption limit established, the vast majority of medical professionals will advise you that safest amount of cannabis to consume while pregnant will always be zero.

Unlike alcohol or illicit drugs, cannabis is not associated with severe birth defects or withdrawal symptoms after birth.

However, when it comes to a baby, it’s always better to play it safe than sorry.


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