sounds like blood flow problems maybe little clots, talk with the dr about it and maybe get some of those support hose
its possible it is just chloasma, which is also known as the pregnancy mask. If that is what it is, then it will go away afternoon childbirth. If she isn't in any pain or discomfort I wouldn't worry about it, just make sure to remember to bring it up at her next appointment.
Where on the body? If below the waist in a line up and down, it's totally normal. Also chlosama, which is on the face, is also normal.
Being low on calcium can also cause bruised-looking skin.