Planking is a very effective way to build up that lost core strength provided you use appropriate modifications. New mums, even those with abdominal separation (diastasis recti) can benefit greatly from this.
But a word on caution here, please be careful to not jump into exercises that your core is not strong enough for. Even if you think you are taking a step back in doing an easier version, do so in order to properly engage the core and breathe well while holding the pose.
This version of the plank is great as it doesn’t put undue strain on those wrists already tired from carrying the baby.
Begin on hands and knees with your abdominals engaged.
Walk your hands out to the front and then release the forearms on the mat. Elbows beneath the shoulders.
Keeping the abdominals engaged, stretch the legs one at a time to the back so the toes/balls of your feet are on the mat.
Try to keep the hips down so that you make a flat line. Picture a cup of water balancing on your lower back. Do not let it tip over.
Squeeze your buttocks and hold the pose for 30 seconds to a minute.
You can bring your knees down at any point of time or several times to reach an easier version of this pose.