Complex congenital heart disease means several heart structures are malformed at birth, so oxygen-rich and poor blood mix or the heart must pump against impossible odds. Symptoms start early and snowball fast.

Blue color is the first clue. Lips, tongue, or fingertips look dusky or deep purple, especially during feeding or crying.

Fast, labored breathing is constant. Babies breathe more quickly than normal and may grunt with each exhale.

Poor weight gain follows. Infants tire at the bottle, fall asleep mid-feed, and don’t add ounces like their peers.

Heart murmur is loud. A harsh, washing-machine sound is heard even without a stethoscope.

Sweating and cold hands appear during feeds. The body works overtime to move blood, so skin feels cool and damp.

Sudden deeper blue spells or fainting mean the blood flow is critically low—an alarm that the heart is failing.