Parenthood, Planned. "What Is the Effectiveness of Birth Control Pills?" Planned Parenthood, www. plannedparenthood. org/learn/birth-control/birth-contr ol-pill/how-effective-is-the-birth- control-pill.

99%

But can be 91% if you consider factors like missing pills.

Explanation:Birth control pills are drugs taken to prevent pregnancy.

If you use birth control pills perfectly, the pill's effectively can be 99% but because human beings have differences and imperfections and the tendency to forget or miss pills — birth control pills can be only about 91% effective. That is to say that 9 out of 100 pill users get pregnant each year.

Ideally,birth control pill is 99% effective,but certain factors can reduce the pill to about 91%,and this is the reality because women are not perfect and consistent in talking birth control pills,that means 9 out of every 100 persons using pill get pregnant each year.

Not taking the pills everyday is the main factor that makes birth control pill to be less effective.

Other factors that affect the effectiveness of birth control pill includes;being overweight,taking some form of antibiotics example; Rifampin, taking antifungal drug like griseofulvin, taking some form of anti-seizure medications, certain HIV medications, and having diarrhoea or vomiting for more than 48hours(2days),

is it multiple choice?

what are the choices?