I tried many different prenatal yogas in Portland, and most of them are just watered down hatha: not helpful for pregnancy or preparing for birth and new baby!
The best ones I found to help for those were Moving Through, in SE, and the Kundalini prenatal at Zenana. Both were very powerful for relieving stress and energizing me during pregnancy, and for getting strong for birth. Both were taught by doulas, also making a big difference. I really wouldn't waste money on the ones that are just basically stretching. They even made me feel more sleepy. These other ones were really great, and I couldn't make it through the week without at least 2 classes, as my pregnancy went on.