Some drugs reduce the effect of the Pill and can cause [[breakthrough bleeding]], or pregnancy (together with [[unprotected sex]], of course). These include [[antibiotics]], [[barbiturate]]s, [[phenytoin]] and [[carbamazepine]]. The traditional medicinal drug [[St John's Wort]] has also been implicated.
When starting to take the birth control Pill some women report slight [[weight gain]], although this depends entirely on the individual and some people experience no weight gain at all while people who are already [[obesity|obese]] or overweight may continue to gain weight. Some people also notice changes in the intensity of [[sexual desire]], [[vaginal discharge]] and [[menstrual flow]].
Some other common side effects are: [[ nausea]], [[ headache| headaches]], [[ Clinical depression|depression]], [[vaginitis]], [[ urinary tract infection]], changes in the [[breast]]s, [[Dermatology|skin problems]], and [[ gingivitis|gum inflammation]].
==Cautions and contraindications==