To build density and "tightness," you need compound movements that mimic mom-life (lifting kids, groceries, gear):
Pregnancy can lead to "Gluteal Amnesia," where the brain "forgets" how to use the butt muscles because the lower back and quads have been doing all the work [1].
Single-leg work is essential for correcting imbalances caused by carrying a child on one hip [3, 4]. 3. Mind-Muscle Connection