What are the possible side effects of taking the Pill? The Pill has few side effects. Some side effects tend to settle within 2 or 3 months of starting the Pill. During this time some women may experience: nausea breast tenderness or enlargement mood changes breakthrough bleeding headache Other possible side effects that may occur over time include: Skin changes including acne or chloasma (brown discoloration on the face) Change is sexual response Weight gain: studies suggest this is not related to the pill