my aunt swears by this..
http://www.walkathome.com/try-walk-at-home/
she done this 5 days a week she said at first just done the video once a day and its 15-20mins long, then she built up to twice a day, between this and just reducing the portion sizing of the regular foods she already ate, and the timeframe of her last meal making it earlier in the day. and any "late" snacks were just light fruit snacks.. she has gone from high 160lbs to 128lbs in about 4-6months. and shes in her 40's almost 50 years old.. i got to give her kudos for that..
but since its only 15-20mins long it'd be easy to do when the baby is even just taking a small nap