The Pill causes 150 chemical changes in a girl's body. Many of these are not fully understood. Teenagers need to be fit and healthy to withstand air the metabolic changes in their bodies caused by the Pill. Furthermore before prescribing the Pill the doctor needs to know a girl's medical history and any records of family illness. 17 Contraindications - when the Pill should not be prescribed.
Smoking increases the risk factor.
Girls should report to their doctor if they are not feeling well. Another important consideration, although not listed is Physical Maturity. The doctor should be sure the girl is ovulating. A recent study showed that a third of healthy girls aged 18 had anovular menstrual cycles. Both menstruation and ovulation could be suppressed permanently in such girls.