This is great news for all you new moms. Whatever effort you are able to give, the added intensity of pushing a stroller in your workouts means increased benefit to you! When pushed correctly and with a neutral posture, you gain great core strength and upper body stability. Don't judge yourself on how much speed you can give soon after the birth of your baby, focus more on consistency. The good news, as well, is that as you get fitter, your baby grows...they become your built in challenge in that stroller.
Grab your stroller, your little one, get busy and have fun!