Guidance on proper form for lunges during exercise while pregnant from Oh Baby! Fitness. Lunges lift and tighten the butt, but they also offer an opportunity to work the pelvic floor. You can do Kegel exercises while doing lunges. Lunges also strengthen quads, hamstrings and glutes. Go to http://www.ohbabyfitness.com for more safe exercise tips for new and expectant moms.