The verdict hasn’t come in on the effect of plant-based cannabinoids on pregnancy and the developing child, though at this stage, it is clear that the endocannabinoid system (ECS) is directly involved in balancing the chemical messengers that are critical to fertility and breastfeeding. The research available on the potential benefits and risks of prenatal exposure are limited and in some cases, quite contradictory.
In a 2017 landmark review of the available research on medical cannabis for many health concerns, which was published in the National Academy of Sciences, , concluded that smoking high-THC cannabis has been linked to slightly lower infant birth weights (as has tobacco use), but that its relationship to other pregnancy and childhood outcomes is unclear. In a 2002 survey of 12,060 British women, researchers were unable to find any significant differences in growth among newborns exposed to cannabis in utero as opposed to those with no exposure when they controlled for other co-founding factors such as the mother’s age, pre-pregnancy weight, and the self-reported use of alcohol, tobacco, caffeine, and other illicit drugs. 
A significant amount of the challenges in this area are related to the difficulties of controlling alcohol and other substances and the legal sanctions that women could face in certain geographical locations for admitting to cannabis use while pregnant. Because of this, a large amount of the medical data covering the implications of maternal cannabis use and its health implications continue to be limited to historical texts, and research conducted from non-Western cultures where the use of cannabis has greater social acceptance, and retrospective survey data. 
Cannabidiol (CBD) on its own hasn’t had enough research for use during pregnancy, and neither have most cannabinoids. A significant amount of the research has focused on THC, in fact, almost all of it. And not all of this research properly controlled for the use of alcohol or other substances, which skews the study results further. Those studies that do control for other substances, many report that cannabis’s apparent impact on birth weight and other adverse perinatal outcomes is minimal. In animal studies involving rodents being given large doses of synthetic THC, adverse reproductive outcomes have been reported. For more information on fertility and conception, read our article on reproductive health.
There have been some studies that have shown no effect from cannabis use during pregnancy on long-term fetal and child development,  with one study even going as far as to report that cannabis has a positive effect on infant health, mood, and milestones,  a 2002 review of the studies reported measurable differences in relation to attention/impulsivity and complex problem solving in children over three years old whose mothers were heavy users.  In a 2014 study conducted in the laboratory, researchers reported that the neurological development of fetuses exposed prenatally to high doses of THC is altered in the area connected to this type of brain activity. 
Although the impact of cannabis use on pregnancy and fetal development remains marginally understood by science and continues to remain a source of controversy, women report anecdotally that very small micro doses of specific ratios and strains of cannabis are effective in bringing relief to nausea, depression, and anxiety during pregnancy.
The historical use of cannabis for pregnancy related ailments such as nausea, reflux, and sleep issues like insomnia are also referenced in African, Indian, and Southeast Asian cultures.  The isolated component of cannabis, CBD, made into what is called, CBD oil, has only reached the wider population in recent times. Cannabis was also a common staple of Western midwives pharmacopeia in some periods in history. Alongside this, it has been shown as an effective pain and anxiety reliever during labor in some women.
If the thought of women using cannabis-based products during labor sounds “out there”, it should be noted that narcotics commonly used for these same purposes in many hospitals include Fentanyl or other similar opioids, including morphine. And the large majority of women in the United States receive epidural medication such as bupivacaine and other synthetic derivatives of cocaine.  All of these have rare but potentially dangerous side effects.
A large scale review of the available evidence was completed in 2016 that also concluded maternal cannabis use (with unknown THC or CBD levels) was not associated with adverse neonatal outcomes such as preterm delivery or low birth weight. The researchers of the study concluded that the risk previously associated with maternal cannabis use seemed to be associated with the use of alcohol, tobacco, or other drugs at the same time.  The more long-term effects of heavy prenatal exposure are more nebulous. A variety of studies have shown lower test scores for school-aged children who were exposed prenatally to high-THC smoked cannabis but were limited to groups with low socioeconomic status and numerous other compounding factors,  meaning, this makes it more difficult to determine the cause. People living in lower income areas can tend to engage in more drug and alcohol use, thus, it becomes harder to control for other factors.
In saying this, pregnant women and health care practitioners must be mindful of possible risks and are advised to err on the side of caution with all cannabis items, and especially avoid synthetic cannabinoids, and high-potency THC products, such as “marijuana”.
One of the most well-researched areas of cannabis, is in its use as an anti-emetic (anti-nausea and vomiting), with it regularly being used in palliative care. In saying that, preclinical research reveals that CBD may be an effective option for nausea and vomiting produced by chemotherapy or other treatments. As for during pregnancy, the research just doesn't exist yet.
Pregnant women can try ginger (taken as a tea, capsules, smoothies, or in food), acupressure bracelets, acupuncture, chamomile tea, peppermint tea (avoid during breastfeeding as it can reduce supply), or vitamin B6. These are considered generally safe options for the body during pregnancy.
In 2002, Dr. Wei-Ni Lin Curry published a first-person account documenting her own use of therapeutic cannabis to alleviate symptoms of hyperemesis gravidarum (HG), a potentially life-threatening condition for both mother and baby characterized by severe nausea and vomiting, malnutrition, and weight loss during pregnancy.
(While general nausea and vomiting, colloquially known as “morning sickness,” is experienced by an estimated 70 to 80 percent of all expectant mothers, approximately 1 to 2 percent suffers from the persistent vomiting and wasting associated with HG.)
“Within two weeks of my daughter’s conception, I became desperately nauseated and vomited throughout the day and night,” Dr Curry wrote. “I vomited bile of every shade, and soon began retching up blood... I felt so helpless and distraught that I went to the abortion clinic twice, but both times I left without going through with the procedure.. Finally, I decided to try medical cannabis… Just one to two little puffs (a micro dose) at night, and if I needed it in the morning, resulted in an entire day of wellness. I went from not eating, not drinking, not functioning, and continually vomiting and bleeding from two orifices to being completely cured... Not only did the cannabis save my life during the duration of my hyperemesis, it saved the life of the child within my womb.”
Canadian survey data published in 2006 reported that cannabis is therapeutic in the treatment of both morning sickness and HG. Of the eighty-four women who responded to the anonymous questionnaire, thirty-six said that they had used cannabis intermittently during their pregnancy to treat symptoms of vomiting, nausea, and appetite loss. Of these, 92 percent said that cannabis (inhaled or ingested) was “extremely effective” or “effective” in combating their symptoms.
A 2018 study published in the Journal of Pediatrics evaluating the effects of cannabis use before, during and after pregnancy (including breastfeeding) involving women living in Colorado, a state that has had long-standing legalized medical marijuana and recreational use, found a 50% increased likelihood of low birth weight in prenatal cannabis use, but did not find any significant differences in gestational age, preterm birth, or neonatal intensive care unit admission, independent of prenatal tobacco use. The authors concluded that, “our findings underscore the importance of screening for cannabis use during prenatal care and the need for provider counselling about the adverse health consequences of continued use during pregnancy and lactation.” 
A more recent 2020 study published in the Medical Journal of Australia involving 5610 pregnant women, 314 of which had reported using cannabis in the three months before or during their pregnancy (none of which used tobacco).
Compared with babies of mothers who had never used cannabis, infants of those who still used it at 15 weeks had a lower birth weight, smaller head circumference, and shorter gestational age (meaning they spent less time in the womb), and other unwanted birth outcomes. Researchers concluded that, “continuing to use cannabis during pregnancy is an independent risk factor for poorer neonatal outcomes.” 
A 2020 study titled, “Considerations and Implications of Cannabidiol Use During Pregnancy” is underway to investigate and create a more detailed understanding of cannabidiol (CBD) and its effects of pregnancy. CBD is non-psychoactive and currently used as a self-medication for a wide variety of conditions such as anxiety, depression, nausea, and chronic pain. It is widely and legally available throughout the United States and many other countries either by prescription or over the counter. Because of this, more research is needed on its effects during pregnancy and on neonatal outcomes.
To conclude this article, we will reiterate an earlier paragraph; pregnant women and health care practitioners must be mindful of possible risks and are advised to err on the side of caution with all cannabis, and especially avoid synthetic cannabinoids, and high-potency THC products, such as “marijuana”.
This article is part of our Women's Wellness series: