Is smoking weed in your first trimester (5 weeks and on) harmful to the baby? are there any known facts that's it's harmful? smoking once a day not all day.

Yes: Smoking weed is harmful to the child and harmful to yourself. It can cause symptoms similar to schizophrenia...!

Yes it's harmful: There are plenty of known facts that marijuana is harmful in pregnancy. For one thing, it can harm the placenta -- that's what nourishes your baby while it's in utero. http://www.sciencedaily.com/releases/2012/09/120912101806.htm research also shows more likelihood of deficits in school achievement, trouble with problem solving, memory, planning, impulsivity, attention, & depressive symptoms.

Learning disability: Smoking marijuana during pregnancy may have lasting behavioral and emotional effects on your baby. Although studies in humans have shown no absolute effects from drug use; differences in potency, composition and quality of the drug can have a profound effect on an unborn fetus. Research on rats exposed to marijuana in utero showed learning problems as the rats matured into adulthood.