Interrupted aortic arch is a birth defect where the aorta is completely split, so blood to the lower body must detour through a small vessel that soon closes. Symptoms start in the first days of life and snowball fast.

Gray or blue color is the first clue. Babies look ashen, especially the lower half, and lips can turn dusky when they cry.

Fast, labored breathing is constant. The infant uses more breaths per minute and may grunt with each exhale.

Weak or absent pulses show up in the legs. You can feel a good pulse in the arm, but the groin or ankle pulse is faint or missing.

Poor feeding and sweating appear early. Babies tire at the bottle, fall asleep quickly, and bead sweat on the forehead.

Blood pressure is high in arms and low in legs. A cuff on the ankle reads much lower than on the arm.

Sudden collapse can happen when the detour vessel closes—an emergency that needs immediate surgery.