Pregnant or not, the banded hip thrust is a great move to strengthen the booty, hips, core & pelvic floor.
This movement can be performed with or without a mini band around the knees and/or on the floor as a bridge if a ball is not available.
Strong glutes = strong core & pelvic floor. Maintaining strength & stability can help reduce lower back pain amongst many other benefits.
Strong glutes are suuuuper important for everyone, especially during pregnancy if the goal is to minimize pregnancy related discomforts.