Dear Casandra,
It is not advisable doing yoga with the help of a book especially when the time of preganancy. In my opinion it will be same as trying to study swimming with the help of a book or a postal coching. A lot of books are available. Even you can purchase on line.
1) Yoga for Pregnancy by Rosalind Widdowson (amazon.com)
2)Yoga for Pregnancy: Safe and Gentle Stretches by Sandra Jane Jordan
Hope this may help
Love
Rajendran
