In the US, about 12% of babies are born prematurely each year. There are a number of risk factors that increase a mom's chances of having her baby early, including previous preterm birth, smoking, preeclampsia or other pregnancy complications, and infection. A new study published in the online journal PLoS ONE adds marijuana use to the list of risk factors for prematurity.
The study, which looked at over 3,000 first time moms, found that smoking marijuana before becoming pregnant doubled a mom's risk of spontaneous preterm birth. Other risk factors included a family history of preterm birth, short stature, and fertility treatments.