What are some good fitness tips for pregnancy?

Aerobic exercises. Aerobic exercises are great for pregnancy -- walking, stair-machine, recumbent or upright bicycle, swimming, low-impact aerobics. Clinical studies have also shown women who exercise have fewer problems with excessive weight gain during their pregnancies and also easier labors!
Low-impact aerobic. National guidelines recommend that healthy pregnant women get 150 minutes per week of moderate-intensity aerobic physical activity like walking. If you've done vigorous activity before pregnancy like running it's probably ok to continue, but check with your health care provider first. Check out this site for more info: http://www.Cdc.Gov/physicalactivity/everyone/guidelines/pregnancy.Html.