Anovulatory cycle
While the normal menstrual cycle in the human typically lasts 4 weeks (28 days, range 24–35 days) and consists of a follicular phase, ovulation, and a luteal phase, followed by either menstruation or pregnancy, the anovulatory cycle has cycle
lengths of varying degrees. In many circumstances, menstrual intervals are prolonged exceeding 35 days leading to oligomenorrhea (cycle >35 – 180 days interval), or even longer, amenorrhea. In other cases, menstruation may be fairly regular (eumenorrhea), or more frequent (intervals < 21 days), or there may be a loss of menstrual pattern (menorrhagia, dysfunctional uterine bleeding).
Natural Cycles
The most recent published clinical study showed that natural cycles, when used correctly, is as effective in preventing pregnancies as the contraceptive pill.
The study analysed 22,785 women through a total of 224,563 menstrual cycles across a year, to calculate the app’s Pearl Index – the rate used to measure a contraceptive effectiveness. It found that if used perfectly – using protection such as condoms on red days – effectiveness is 99 percent. Typical use, where people become pregnant for all possible reasons, leads to 93 percent effectiveness. This is well above other Fertility awareness based methods that rate at around 75 percent and even the contraceptive pill, which rates at 91 percent. Further studies include the “Identification and prediction of the fertile window using Natural Cycles" and “Fertility awareness-based mobile application for contraception”. For the app to remain effective, women need to follow the app's instructions correctly, and it does not protect its users from sexually transmitted diseases.