Final answer:
Vaginal discharge or bleeding in female infants under 3 months old often results from maternal hormone withdrawal, but could also indicate infection, trauma, or more serious conditions which require immediate medical evaluation.
Step-by-step explanation:
In cases of vaginal discharge or bleeding in female infants younger than 3 months old, a medical professional would consider several potential causes. The most common is maternal hormone withdrawal, which can lead to a mini "period" known as pseudo-menstruation. This is due to the decline of maternal estrogen in the baby's bloodstream after birth. Other causes could include infection, trauma, or a foreign body in the vagina. More serious, but rare, possibilities would involve disorders of sexual development or tumors. It's important for a physician to evaluate the infant to rule out any serious conditions.