If you have children, bring them in the stroller or ask them to follow along on their bikes if they are older. All you need is a pair of shoes and a water bottle. On hot summer days, you can workout but it’s important to drink twice as much water. Here's a 4-week program which includes 3 or 4 walking sessions per week as well as some yoga exercises that you can replace with muscle strengthening exercises.
You can use this sample workout throughout your pregnancy, lengthening or shortening the duration of the sessions according to your requirement, or by adding interval training (see below training example).
To vary the walking exercises, you can play with the duration, intensity, or the choice of terrain. Here are some simple examples offering alternating fast walking with slower walking. Brisk walking can be done at a high intensity, which is at 5 or 6 on the adapted BORG scale, and walking at a moderate intensity, which is 2 or 3 on the adapted BORG scale.
And here are estimated numbers of calories burned for an hour of walking, depending on the walking intensity.