Adrenal Cushing syndrome during pregnancy is rare, and there is limited information on the effect and safety of metyrapone treatment both for mother and fetus. We present a 24-year-old woman diagnosed with adrenal Cushing syndrome at the end of the second trimester. We elected treatment with metyrapone titrated to 250 mg 3 times daily, resulting in good clinical response and maternal serum and saliva cortisol levels in the upper half of the normal pregnancy range. A healthy male infant was born at 35 weeks' gestation, with no clinical signs of adrenal insufficiency, this despite a low cortisol of 5 nmol/L on the first day of life. We measured metyrapone in maternal and umbilical cord blood samples, demonstrating fetal venous metyrapone levels similar to maternal venous concentration, and a fetal arterial cord concentration at about 60% of the fetal venous cord concentration. This case demonstrates that salivary cortisol levels may be used to monitor the effect of metyrapone on adrenal Cushing syndrome during pregnancy. We show, for the first time in humans, that metyrapone does cross the placenta and may suppress fetal cortisol production without necessarily causing clinical signs of adrenal insufficiency.