When I was researching morning sickness remedies I came across a bunch of posts where women were managing their morning sickness with cannabis. What?! Really?! Of course I had to look into the ill effects of smoking weed/pot/marijuana/bit o' the bumble while pregnant because I just had to know, plus, the question was harshing my buzz (just kidding).
Marijuana contains more than 400 chemicals including tetrahydrocannabinol (THC), which is rapidly absorbed from the lungs into the bloodstream and is metabolized primarily by the liver. It does cross the placenta.
Although marijuana is not an established human teratogen, recent studies suggest it may contribute slightly to sleep disturbances, impaired visual problem solving and hyperactive, inattentive, and impulsive behaviour. So kids that are a little batshit.
On the flip side, a study was conducted in Jamaica, where the women who used the large doses of marijuana were better educated and more independent than women who consumed the small doses of marijuana. The one-month old infants of the heavy marijuana-using mothers had better scores on autonomic stability, quality of alertness, irritability, and self-regulation. It's suggested that these differences related to the characteristics of the mothers using marijuana rather than the marijuana itself.
I found it interesting that when there are ill effects, it is attributed to the drug but when there are positive effects, it's attributed to other factors in the study but I digress.
As mentioned above, isolating the effect of cannabis from other factors (e.g., social and economical factors, nutrition, and the use of other drugs) is difficult so it's unlikely there will be much more information until someone can legally make a lot of money off cannabis like a pharmaceutical company (or the Keebler Elves).
In short, none of the studies show any significantly difference in spontaneous abortion, birth weight, malformation or postnatal mortality but I'm not sure how reassuring that is.
On a side note, I found an interesting study that was done on pregnant rats where the offspring of the rats that were administered high doses of THC in sesame oil had impaired nipple attachment. Then they figured out that it may be because they didn't give those rats enough food or water. Er, okay. Why do I feel like those guys just smoked half the study then forgot to feed the rats? "Dude, when was the last time those pregnant rats had water? You know what would be cool, is if we could train the rats to do our thesis. Write that down, man. Are there any chips left? Awesome."
search: marijuana pregnancy, delta-9-tetrahydrocannabinol pregnancy