What adverse effect should the nurse inform a client about when prescribing an oral contraceptive?

Breakthrough bleeding is a common adverse effect that can occur with the use of oral contraceptives. This phenomenon can happen when the hormonal levels fluctuate and may not provide sufficient support for the uterine lining throughout the menstrual cycle, leading to unexpected bleeding or spotting between periods. Informing clients about this potential effect is crucial for managing expectations and encouraging adherence to their contraceptive regimen.

In contrast, menorrhagia refers to excessive menstrual bleeding, which is not commonly associated with oral contraceptives, as these medications typically help regulate and lighten menstrual flow. Constipation is not a typical adverse effect of oral contraceptives, and while hormonal changes can influence bowel habits, it is not a direct or well-documented side effect. Oligomenorrhea, which is infrequent menstruation, might also occur with oral contraceptive use as they often lead to lighter and less frequent periods, but breakthrough bleeding is more immediate to anticipate as a side effect upon starting the medication.