It's designed to accommodate a growing baby bump during pregnancy, and thanks to the layered cut - out, it's perfect for postpartum breastfeeding as well! (tinyfry.com)
There is also expandable unit design that accommodates growing babies in easy way. (thankyourbaby.com)
It also stands to reason that the heart will have to pump blood that much faster to accommodate the growing babies inside of her. (babygaga.com)