Having a baby is horrible for your core strength! Your abs become unusable for a while and your lower back gets a severe curve in it from the weight of your belly. Then, once you have the baby, your upper back and shoulders start to curve around in order to hold baby and milk-filled breasts make you want to slouch over. But with some awareness and effort, you can fix this. A swiss ball, or exercise ball, will be a huge help. And once you feel Baby is strong enough, you can even use him/her as a counterbalance while you do your exercises. I started off just on the bed, doing some leg extensions and bicycle motions. This helped my muscles find themselves again, which is the first step to getting them to engage in daily activity. It is strange when you realize you no longer know how to activate particular muscles, but doing exercises which will force them to be used will solve this.