“Analyses failed to support any significant relationship between marijuana use in the third trimester and a variety of maternal and infant outcomes.

Preliminary results indicate that marijuana exposure in the third trimester does not complicate the pregnancy or the delivery process.” https://www.ncbi.nlm.nih.gov/pubmed/28917206

http://www.drugandalcoholdependence.com/article/S0376-8716(17)30443-X/fulltext