WebMD states that Yaz has several common side effects, including the absence of menstrual periods, irregular periods and bleeding not related to a menstrual period. RxList explains that these side effects are mild, common for birth control pills and typically decrease with time.
WebMD lists other potential side effects for Yaz, many of which are severe. Infrequent side effects include migraine headaches, high blood pressure, head pain, low energy, weight gain, nausea and mood changes. Rare side effects include depression, stroke, blood clots and water retention. RxList further explains the consequences of blood clots and suggests that patients discuss their risk for blood clots before choosing a birth control.