Anesthesia and surgery in a patients with undiagnosed or untreated hypothyroidism can carries the risk of potential complications such as prolonged unconsciousness, respiratory insufficiency, hypotension, hyponatremia, congestive heart failure, and even coma. A 33-year-old gravida was admitted at 36 weeks gestation with hypertension, proteinuria, generalized edema, and intrauterine fetal growth retardation. She had thyroidectomy for thyroid mass six years ago. Because of doubt of uterine abruption, emergency cesarean section was performed without result of thyroid function test. Preeclamsia and mild hypothyroidism show similar symptoms and it can make difficult to diagnose hypothyroidism. We experienced delayed recovery and respiratory insufficiency in a patient with preeclamsia and undetected hypothyroidism during emergence from general anesthesia. She was fully recovered after ventilatory care in intensive care unit.