Total anomalous pulmonary venous return (TAPVR) sends all oxygen-rich lung blood to the wrong place—usually a vein behind the heart instead of the left atrium. A baby can survive only while a small fetal tunnel stays open, so symptoms explode in the first days of life.

Blue color is the first clue. Lips, tongue, fingers, and toes look dusky or deep purple, especially when the baby cries or feeds.

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

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

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

Weak or absent pulses can show in the legs if the ductus is closing.

Sudden collapse can happen when the fetal tunnel closes—an emergency that needs immediate surgery.