Phantom lady-GOOD FOR YOU. The fact that you've cut down should be commended. Cigarettes yes are harmful to both of you, but cutting back the way you have is very difficult and what awesome dedication you have to your baby! Congratulations by the way.

I have been assisting with deliveries of babies for nearly 10 years now and have done some of my own research into the benefits and effects of marijuana use during pregnancy. I've received most of my info from honest midwives who aren't in fear of being sued, from medical books and also from direct experience (Unfortunately most women will not admit to smoking marijuana during pregnancy). Of course overuse of anything can be harmful, mostly from partaking by smoking the plant. Use moderation in anything you do. If you can find organically grown plants, you and your baby are much better off. You should always be aware of the pesticides being used on the plants.
Also as far as any birth defects, the majority of pharmaceuticals an MD will prescribe women during pregnancy for nausea, pain (including pain meds used during childbirth), etc. have been shown to not be completely safe for human fetuses. They are mostly 'category B: Animal studies show no risk but there are no controlled studies in women, or animal studies indicate a risk but controlled human studies fail to demonstrate a risk. Heparin and penicillins fall into this category.' Or
'Category C: no adequate studies, either in animals or women, are available, or animal studies show teratogenic (factors that can produce malformations of the fetus) effects but no controlled studies in women are available.' (This is a classification developed by the FDA for healthcare professionals).
So, if you need something for pain or nausea or decreased appetite or sleep, smoke your plants. 'To date, there is no evidence that marijuana has any teratogenic effects' (Niebyl JR: Teratology and drugs in pregnancy and lactation. In 'Danforth's Obstetrics and Gynecology'). And it's been around longer than any of these pharmaceuticals. Be aware however that some MD's are not open minded about this, it is in fact still illegal, and will have you drug tested if you admit to 'using'. Do whatever feels right to you but there will probably not be any reason to disclose this to your doc. And check if your community allows midwives to deliver babies in the area hospitals-they are typically not as busy as MD's and can offer alternative therapies to many aspects of pregnancy and birth. Most importantly-stay informed and ALWAYS ask LOTS of questions!
Take care of your body, remember your womb is the baby's first environment. Drink your (purified) water!! And enjoy your pregnancy and the birth of your new life. No worries (fetuses sense stress).
(Sorry, didn't mean to write a short story, I happen to think this should be public knowledge)