Is it safe to drink decaf tea during pregnancy?

Yes, decaffeinated teas and even decaf coffee are safe to drink.

Caffeinated teas are even safe to drink during pregnancy, in moderation. The amount of caffeine in a typical cup of tea is much less than that in a typical cup of coffee. The current stance of the American Congress of Obstetricians and Gynecologists is that up to 200mg of caffeine daily is totally safe during pregnancy. This is enough for 1-2 cups of coffee or 3-5 cups of tea, depending on how strong it is.

Even higher amounts are going to be much safer than, say, smoking or alcohol consumption. Moderate tea and coffee drinking is not worth worrying about, although tea is probably a safer bet as it is much lower in caffeine.
Yes u can. U can actually drink 3-4 cups of normal tea but i wud suggest decaf cups 3-4 are gud.