Must the vow to slaughter a goat be fulfilled if the newborn suffers from a mild disability that can be cured?

One who makes a conditional vow is not obligated to fulfill anything unless the condition upon which their vow was suspended is met. So, if you vowed to slaughter an animal upon being blessed with a healthy child, and disability contradicts health, then nothing is obligatory upon you unless you intended health apart from this disability or similar conditions. A conditional vow is disliked.