As far as the tea bags, you can start with one bag and gradually work up to 4-6 bags by 27 weeks, Then its good to use at least 9 bags per day by 35 weeks until delivery. The 9 bags per day is recomended by a midwife from 35 weeks to delivery. It is more expensive using bags!
IF you want to use teabags, I have measured out on my scale how much herb is in each bag for doing Susan Weed Style infusions (steeped 4 hours)
Yogi Tea bags:
4 bags aprox...