Menstrual cycle
The menstrual cycle is the regular natural change that occurs in the female reproductive system (specifically the uterus and ovaries) that makes pregnancy possible. The cycle is required for the production of oocytes, and for the preparation of the uterus for pregnancy. Up to 80% of women report having some symptoms during the one to two weeks prior to menstruation. Common symptoms include acne, tender breasts, bloating, feeling tired, irritability and mood changes. These symptoms interfere with normal life and therefore qualify as premenstrual syndrome in 20 to 30% of women. In 3 to 8%, they are severe.
The first period usually begins between twelve and fifteen years of age, a point in time known as menarche. They may occasionally start as early as eight, and this onset may still be normal. The average age of the first period is generally later in the developing world and earlier in developed world. The typical length of time between the first day of one period and the first day of the next is 21 to 45 days in young women and 21 to 35 days in adults (an average of 28 days). Menstruation stops occurring after menopause which usually occurs between 45 and 55 years of age. Bleeding usually lasts around 2 to 7 days.
The menstrual cycle is governed by hormonal changes. These changes can be altered by using hormonal birth control to prevent pregnancy. Each cycle can be divided into three phases based on events in the ovary (ovarian cycle) or in the uterus (uterine cycle). The ovarian cycle consists of the follicular phase, ovulation, and luteal phase whereas the uterine cycle is divided into menstruation, proliferative phase, and secretory phase.
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.