I looked them all up, and can't for the life of me think of any complications that may arise from taking these herbs while pregnant. Like you said though, maybe they don't have publicized studies on the effects.
My only main concern is that they all have diuretic properties, so you will want to make sure you are well hydrated all the time!
I found it interesting though, in my book it said that some cultures consider artichoke to be an aphrodisiac!
Just be sure to stay moderate in your consumption.