There is evidence of cognitive deficits related to in utero exposure to cannabis. These effects include IQ deficits, inattention, lower verbal reasoning scores, memory issues, ADHD
, higher rate of psychiatric illness, etc. However there is no evidence of very serious malformations, or risk of fetal loss. As an addiction specialist, I would be more worried about the effects cannabis use would have on the mother, and therefore on the care of the baby.
I recommend you stop using cannabis immediately. I would not consider it harmless for a fetus or breast-feeding infant. There are far too many medicinal and natural remedies for nausea
to justify the risk of cannabis use.