There was some promising news last week for expecting mothers wanting to curb their morning sickness with a puff of purple kush. LiveScience published an article titled “Using Pot While Pregnant Not Tied to Birth Risks” reporting the results of a study which showed exactly what the headline makes it sound like.

The only problem is that the “results” from this study weren’t the most scientifically precise. What some statistician peeps did is they compiled the results of 31 previous studies on the relationship between cannabis and birth complications. 7,800 women factored into the data. At first, it was looking bad for stoned pregnant women. Results showed that those who sipped the ganj while waiting for the stork to arrive were found to be 43 percent more likely to have a baby with a low birth weight, and 32 percent more likely to get a preterm birth.

But then the statisticians did some rejiggering of the data. They adjusted the results to filter out those women who also drank alcohol or smoked during pregnancy. When they did that, the birth risks correlated to puffing the magic dragon went down to zero. Great. So, now we can give an eighth of sour diesel as a present next time we’re invited to a baby shower.

But not so fast. Some party poopers are saying that these conclusions might be a little hasty, and the study they’re based on a little weak. “When the authors go from the adjusted analyses to the further adjusted analyses, they have to dramatically reduce their sample size,” Aaron Caughey, MD, chair of the Department of Obstetrics and Gynecology at Oregon Health & Science University in Portland, told Forbes. “Thus, the negative findings of no increased risk for preterm birth or low birthweight could just be because of inadequate study power.”

Okay, so what do we actually know about the effects of cannabis on an unborn fetus? Not much, as it turns out. The study, which was published in Obstetrics & Gynecology, was explicit about the fact that it had nothing to say about the long-term neural effects of a pothead mom on the baby inside her, and also professed that its results “do not imply that marijuana use during pregnancy should be encouraged or condoned.”

They’re basically saying they don’t know anything, but it gets worse. It seems we actually know less than nothing. We don’t even have a ballpark guesstimate for how many pregnant women are using cannabis (Forbes puts it between 2 and 27 percent, a canyon-like margin). We don’t even know what the pregnant women who use marijuana mean when they say “use.” Are they smoking it, vaping it, dabbing it, eating it, or topical ointment-ing it? Do they use once a month, once a day, or all day e’ry day?

We don’t know. But there is a Swedish study from 2014 that shows that THC exposure to a fetus could disrupt the development of nerve cells in the brain, so maybe lay off the endo until your nine months are up if you want to play it safe.

Photo via Flickr user Cody