Cushing's syndrome is a rare condition in the general population (1/1000000) and is even less common during pregnancy. We report the case of a patient cared at 27 weeks of gestation (wg) for hypertension and electolyte disturbances. Cushing's syndrome was confirmed by salivary cortisol and ACTH assessment. RMN revealed a 9 cm left adrenal tumor. Severe hypertension and electolyte disturbances on the one hand, and diagnostic uncertainty on the other hand, imposed adrenalectomy at 29 wg. Twelve days later, fetal distress led to a caesarian section and birth of a well being male baby.