You're pregnant and miserable with nausea and a body full of mixed-up hormones. Can you safely use cannabidiol (CBD) for morning sickness, anxiety, and other health issues? The answer is short—nobody knows for sure yet. This is mainly because it's a difficult subject and population to study—for understandable reasons—and data is very sparse.
However, some studies have been done in laboratories, animals, and human pregnant women and their children, so here we attempt to unpack the available research so you can decide for yourself.
Please note that if you're pregnant, it would be advisable to consult with your physician or pediatrician before taking any nutritional supplement, including CBD for morning sickness.
The outcomes of exposure to cannabis have been fairly well reviewed. A 2016 systematic review and meta-analysis conducted by several departments at the University of Arizona in Tucson revealed the following regarding the use of marijuana during pregnancy:
Another 2016 review, looking to demonstrate the effects of marijuana exposure on a developing embryo, was conducted at the Georgetown University Medical Center in Washington, D.C. Here, the researchers noted that cannabis use altered multiple mechanisms in the mothers' bodies, which, they concluded, could result in dire problems. These problems include the following:
In a study conducted on mouse embryos, researchers found that THC inhibited the development of the embryos which contained less than eight cells. Another natural cannabinoid found in the human body, anandamide, also stopped the embryos from developing. Knowing that CBD can increase the levels of anandamide, there may be negative effects associated with CBD use during pregnancy. It is important to note that this was a study conducted on mice and the results may not be transferable to human subjects.
It's important to remember that CBD has been associated with inhibition of cell growth, cell movement, and even cell death. This augurs well for the treatment of diseases such as cancer, for instance, as other studies have shown. 
However, this property has been demonstrated across many cell lines, and as the researchers put it:
"...by the same mechanisms that cannabinoids show promise in the field of cancer treatment, they prove equally dangerous to the viability and health of a developing embryo...The effects of cannabinoids on pre-implantation and embryologic development have the potential to elicit harmful outcomes postnatally." 
Yet another older review into the consequences of maternal marijuana use on the fetus notes that:
".. at birth, newborns show increased tremors accompanied by exaggerated and prolonged startles or altered sleep patterns. In infancy, children exposed to cannabis in utero are more likely to have problems with executive functioning including lower memory scores, as well as more attention problems, hyperactivity, and impulsivity in early childhood."  
In other words, smoking or ingesting THC during pregnancy is associated with neurological problems in children. These issues include poor memory, attention problems, hyperactivity, and impulse control disorders.
These reviews cannot be ignored, so taking cannabis or CBD for morning sickness or any other pregnancy symptom should not be considered lightly.
However, the authors of all these reviews admit that the subject is vastly under-researched and that there are, in fact, numerous problems with the available data.
A few design flaws were inherent in all clinical studies reviewed, which can undoubtedly impact the research conclusions.
The most worrying, however, should be the data on CBD's effect on cancer cells. As previously mentioned, it has been shown to stop cell growth, kill off cells, and prevent tumors from spreading. This has been tested in human cell cultures as well, so it is not far-fetched to argue that CBD could possibly affect fetus cell growth. 
Also, another review looking only at the animal and human studies concluded that the endocannabinoid system plays a very important role in the development of the human central nervous system from gestation onward. Its activation during brain development, says the researchers, can induce subtle and long-lasting neurofunctional alterations. 
There is anecdotal evidence of mothers who used CBD during pregnancy without any apparent effect on their children. Perhaps factors such as the quality of the CBD oil these mothers took, as well as dosage and frequency of use, have made differences not yet spotted by scientists and physicians.
Also, medicines that are now prescribed for pregnant women were previously advised against, such as antidepressants, painkillers, and some anxiolytics. The onus rests on the physician and the mother to decide on the risks.
Yet a lot of questions still need to be answered, and the effect of CBD for morning sickness or any other symptom in pregnant women can never be researched as it ideally should be—with long-term, placebo-controlled, double-blind clinical studies. Hopefully, other related research will pave the way for safe use, as CBD is undoubtedly a safe and very effective remedy for nausea and many other ailments.