How to Tighten Your Stomach After a Pregnancy & C-Section. Part of the series: LS - Women's Power & Core Workout. During a C-section the muscles of the abdominals are pulled apart so it's important to make sure that you work to increase the strength of the core afterwards. Tighten your stomach after a pregnancy and a C-section with help from a fitness and wellness professional with over 12 years of experience in this free video clip.