A sign language interpreter just attended my childbirth educator training. She recommends the DVD series Your Pregnancy, What to Expect. It is signed in ASL with voiceover and subtitles.
There are more details on it at https://www.audiopaccom.com/your-pregnancy-what-to-expect#.VvwJQo-cGM8
It covers prenatal care, prenatal development, exercise, stages of labor, cesareans, interview with pregnant deaf women about their experiences, and info on how to access interpreters.