Relative to body size, your baby's adrenal glands are 20 times larger than your own. The adrenal glands are roughly triangular in shape, with their base wrapped over the top of each kidney. They have an outer layer, or cortex, which releases steroid hormones such as cortisol, and an inner layer, or medulla. Adrenaline and the related hormone noradrenaline are secreted from the medulla in response to stress.

Adrenaline prepares the body for a "fight or flight" response, increasing the availability of glucose, speeding up the heart rate, and maintaining or raising blood pressure. These are vital adaptive responses for your baby that will help to maintain a stable environment within the uterus and prepare her for the stresses of life later on in the outside world.

It is the outer cortex, however, that needs to work hard, producing many hormones that help to coordinate your baby's growth and development. The cortex produces three types of hormones: mineralocorticoids that regulate salt balance; glucocorticoids that help to control the availability of sugars, fat, and amino acids in the bloodstream; and androgens, male-type sex hormones, such as testosterone. It is the cortex that accounts for the large size of your baby's adrenal glands. After birth, in the first couple of weeks, the adrenal glands rapidly reduce in size.