Menstruation is the periodic bleeding of the endometrium under the influence of the ovarian cycle. With ovulation as the boundary, the first half is the follicular phase, and the second half is the luteal phase. The cycle difference mainly depends on the length of the follicular phase. The luteal phase is relatively stable, usually two weeks (14 days).

From the first day of the next menstruation, the last 14 days or minus 14 days is the ovulation day. The ovulation day and the first 5 days and the last 4 days together are called the ovulation period. At that time, it is easiest to conceive in the same room. This is the theoretical basis of safe period contraception.

Tips: This method is not suitable for women with irregular menstruation.

Basic body temperature refers to the body temperature without exercise, eating or mental function. The thermoregulatory center is extremely sensitive to progesterone (also called luteal hormone), and a certain amount of progesterone can cause temperature rise. On the next day after ovulation, due to the formation of corpus luteum by ovaries, progesterone secreted by corpus luteum will increase the body temperature by about 0.6 degrees Celsius, and the high temperature period lasts about 12-16 days. If there is no pregnancy, the corpus luteum atrophy stops secreting progesterone, the body temperature drops, returns to the baseline, and menstruation comes.

Put the basic thermometer under the tongue for five minutes and record it on the basic thermometer before waking up every day.

Tips: (1) More than 3 menstrual cycles need to be measured continuously to explain the problem. (2) If you have irregular menstruation or life, such as night shift, business trip, insomnia, emotional changes, diseases, etc., you cannot use this method to judge whether there is ovulation.

The cervical mucus is controlled by hormones secreted by the ovary. In the first half of the menstrual cycle, the amount of leucorrhea increases gradually. When the follicle matures and will be discharged, the leucorrhea becomes thinner and clearer. During the ovulation period, the estrogen secretion in the body reaches the peak, and the cervical mucus (leucorrhea) is the most. There is often a thin band of leucorrhea flowing out, sometimes stretching up to ten centimeters (that is, the drawing degree), like egg white. At this time, women's lower body is the wettest. During ovulation, a large amount of cervical mucus can be secreted for about 2-3 days. Some women also have (momentary) small abdominal pain, low back acid, and bloody leucorrhea during ovulation. This phenomenon is called ovulation pain.

It takes several times a day to observe the cervical mucus. Generally, you can use your fingers to take mucus from the vaginal orifice after getting up, before bathing or before urinating, and observe the appearance and consistency of the mucus on your fingers, as well as the drawing reaction with your fingers. In this way, after more than 3 menstrual cycles, you can master your own cervical mucus secretion rule and ovulation period. Once it is found that there is a sense of wetness in the vulva and the viscous mucus has a tendency to become thinner. When the mucus can be brushed up to several centimeters, it should be considered to be in the pregnancy period (ovulation period). It can enter the post ovulation safety period until the fourth day after the peak day of the thin, transparent mucus that can be brushed.

Ovulation test paper is also called luteinizing hormone (LH) test paper. Normal women maintain a trace of luteinizing hormone. In the middle of menstruation, the secretion of LH hormone increases rapidly, forming a peak, and stimulates the release of mature eggs in the ovary within 48 hours thereafter. Women are most susceptible to pregnancy during this period.

Test once a day from the 11th day of the menstrual cycle. The urine collected from 10 a.m. to 8 p.m. every day was observed. Put the test paper into the urine, and judge whether ovulation occurs according to the display. （ The test paper should be stored at room temperature and away from light. If it is placed in a refrigerator, it should be rewarming before use ）