Realisticaly the only thing you could take to help would be a good multivitamin such as Solgar Prenatal Vitamins (from a good health store) and make sure you're general diet/lifestyle/stress levels are in good shape.
I thought you couldn't take it from reading a boots bottle too, I had had to pick up a bottle from boots while on holiday in a small town when I came down with a cold last year,(it didn't work, but I think that was probably the boots lack of quaility!!) I still had it in the cupboard and read it when I was first pregnant. I have since read reconmendations that you CAN take it in the right dose though.
Zita West is very good and well respected so if she says in her book that you can take it then I'm pretty sure you can, it's not like she would risk being wrong on such an importatnt thing and say that without knowing for sure.
As Peanuthead says though, I would go to a qualified medical herbalist and speak to them, they will know for sure and they will give you instructions and a correct dose to take during pregnancy. I have recently been to my local herbalist form remedies to help with stress and they were very helpful and spent a long time sorting out just the right thing for in pregnancy.