Repeated use increases risk of the following: Spontaneous abortion Fetal growth restriction Abruptio placentae Preterm birth Stillbirth Congenital malformations (eg, central nervous system, genitourinary, and skeletal malformations; isolated atresias) Although marijuana's main metabolite can cross the placenta, recreational use of marijuana use does not consistently appear to increase risk of congenital malformations or fetal growth restriction.