Long-term family planning and contraception
Unfortunately, pregnancy rates for various contraception methods are presented only as yearly rates, while most of us would like to prevent pregnancy for much longer stretches than one year. Some of these rates are also likely underestimated due to the inclusion of dual method users. Since some of the most commonly used contraceptives become less effective when used over longer periods of time, many women have more children than intended:
…the typical woman using contraception, including sterilization, would have 1.3 unintended pregnancies by age 45. This estimate rises to 1.8 when sterilization is not included. By age 40, 60% of women have faced an unintended pregnancy, not including unintended pregnancies ending in spontaneous loss.
This study extrapolates the pregnancy rates of many methods of contraception, including combined use, over time periods stretching from 5 years to maximum lifetime fertility. These are broken down into a typical and perfect use comparison in a consumer-friendly table. For example, typical use of the pill only over 5 years carries a high pregnancy risk of 20-50%. This increases to over 50% by 10 years. The pregnancy risk of using only condoms for 5 years is also greater than 50% over that time. Check out the table and the methodology, by Aaron Hamlin:
Hamlin, Aaron F., Reframing the Presentation of Contraception Pregnancy Rates: Integrating Long-Term Planning and Dual Methods (April 17, 2010). Available at SSRN: http://ssrn.com/abstract=1591625
