I've attended prenatal yoga for 2 prior pregnancies and this current pregnancy. I would strongly recommend it.
Exercise is good for both you and baby's development.
Just a word of caution, as with all exercises, know your body and yourself.
At present, I am about 7 months plus.
Some days, I am very flexible and can do wonderful stretches and hold poses for long periods, better than even those who are only 3-4 months pregnant.
Some days, I just feel lazy or feel that my body isn't up to it - on those days, I still attend class but take it super easy. Just always LISTEN to your body. During pregnancy especially, exercise including yoga is NOT A COMPETITION (I say this because I am quite, okay, very, competitive and when not pregnant, will always push myself as far as I can, especially if I see a more flexible class member
)
I attend classes at Pure Yoga for all 3. They have prenatal classes 3 times a week.
If you are experienced at yoga, you can also attend normal hatha classes - just avoid the poses which make you lie on your belly or which use a lot of abdominal muscles. Most of the instructors will be able to give you alternate poses to do while the rest of the classes are doing these "barred" poses. Avoid hot yoga classes and higher level classes. If you are not familiar with yoga, suggest you confine yourself to the prenatal classes at least for a month or 2 until you gain some familiarity. Then depending on your confidence level, you can try the "normal" classes. Speak to the instructor before class.
Hope this helps.