Why do your stomic gets hard when your pregnant?

Growing Uterus: When you're not pregnant, your abdomen is filled with soft, squishy intestines. When you are pregnant, the uterus is growing and is much firmer than the rest of your abdomen. By the late 3rd trimester your entire abdomen is basically filled with uterus.

Uterus: You can feel the strong muscular wall of the uterus through your abdomen. Congratulations on your pregnancy.