"I’m six months pregnant and have lower back pain. I’d like to try cannabis to see it can help. "
I am not a doctor, but a HelloMD doctor addressed this very question in a previous question:
To paraphrase Dr. Solomon’s answer, in a University of Adelaide Study "showed that women who use cannabis up to their 20th week of pregnancy have a 5 times higher risk of labor and birth before their 37th week. Of these women, 64% delivered at less then 32 weeks."
Judging by this study which took into account a large control group, it is not advised. You will see a lot of information online to the contrary.
Hope this helps