The hazards of smoking tobacco while pregnant are well-known. Now, researchers have found that prenatal marijuana use also has consequences.
A study by University of Buffalo researchers of more than 250 infants and their mothers concluded that using marijuana and tobacco during pregnancy can cause babies to be smaller and born earlier than babies whose mothers used only tobacco. Infants who were exposed to marijuana and tobacco — particularly in the final three months of pregnancy — were shorter, lighter and had smaller heads at birth. The results were more pronounced for boys than girls.
Researchers say the results are especially timely as more states move toward legalizing marijuana. Nearly 30 percent of women who smoke tobacco during a pregnancy, they noted, also use marijuana.
So why does lower birth size and weight matter? Because it influences a baby’s behavior later in infancy. Smaller infants tend to be more frustrated, more irritable and less able to calm themselves during difficult moments, the researchers noted. That shows there is an indirect link between exposure to marijuana and tobacco, birth size and infant behavior.
It’s all part of a difficult cycle for mom and baby: Expectant mothers who reported more stress were more likely to keep using marijuana and tobacco. That leads to smaller, more irritable newborns.
Researchers say the findings make a good case for helping women who smoke tobacco or use marijuana while pregnant by encouraging them to focus on stress reduction and avoiding negative emotions. A calmer mother-to-be might be less likely to use marijuana, leading to more robust — and tranquil — infants.