If you think that smoking weed while you're pregnant is okay...think again.

Babies are meant to be born without Melatonin and have to rely on their Mother's Breast Milk to get it, the first 3 months, until their Pineal starts producing it naturallly, through Amino Acids.

Smoking Weed raises your Melatonin Levels 4,000%, two hours after smoking a joint.

This is off of Melatonin.com:

Should certain people avoid it?

Yes. "Those include women who are pregnant or nursing (since no one knows how excessive exposure to the hormone might affect a fetus or infant); people with severe allergies or autoimmune diseases (melatonin could exacerbate such conditions by stimulating the immune system); people with immune-system cancers such as lymphoma or leukemia (for the same reason), and healthy children (who already produce it in abundance). Women trying to conceive should also think twice about taking the hormone, since high doses can act as a contraceptive." As with any substance introduced into your body, if you have a medical condition you should always consult your physician first before taking melatonin.