Marijuana doubles risk of preterm birth
Researchers collected demographic and health-related data from more than 3000 pregnant women in Australia and New Zealand in 2004–08, to assess the biggest risk factors associated with birth prior to 37 weeks gestation.
They found that a family history of low birth weight babies was the strongest risk factor for preterm birth. Women with such a history were more than 5.5 times likely to have a premature baby.
Marijuana use prior to pregnancy was the second highest risk factor and women who smoked marijuana before they were pregnant were almost 2.5 times more likely to deliver preterm.