Table 2

Typical-use 1-year PI of Natural Cycles for cohorts of users by method of contraception used prior to Natural Cycles versus expected PI according to population figures

Contraceptive12-Month typical use PI by last method of contraception13-Cycle life table pregnancy probability by last method of contraceptionTypical use PI for previous contraceptive2 Difference in PI
Male condom3.5±0.53.6±1.018↓ 14.5
Withdrawal6.0±1.05.4±1.922↓ 16.0
Copper IUD5.4±1.36.4±3.60.8↑ 4.6
Fertility awareness*7.2±2.17.4±4.624↓ 16.8
None6.5±1.37.0±3.185↓ 78.5
All non-hormonal4.8±0.44.8±0.9
Previous hormonal method (>60 days prior to Natural Cycles)5.6±0.75.8±1.7
Contraceptive pill8.1±0.68.7±1.39↓ 0.9
Hormonal IUD5.3±1.35.4±2.90.2↑ 5.1
Hormonal ring6.2±1.57.1±4.29↓ 2.8
All hormonal (<60 days prior to Natural Cycles)7.6±0.58.2±1.2
  • *Risk varies with specific fertility awareness method. Natural Cycles was not part of this figure.

  • IUD, intrauterine device.