“"Safe period" contraception is unreliable

　　Menstrual period, safe period and ovulation period:

　　Normal women of childbearing age have menstruation once a month. The period from the beginning of this menstrual period to the first day of the next menstrual period is called a menstrual cycle. For example, from the perspective of contraception, each menstrual cycle of a woman can be divided into menstrual period, ovulation period and safe period.

　　Women's menstrual cycles may be long or short, but the interval between the day of ovulation and the start of the next menstrual period is relatively fixed, generally around 14 days. Based on the relationship between ovulation and menstruation, the ovulation period can be calculated based on the menstrual cycle.

　　Calculation method:

　　Counting from the first day of the next menstrual period, the 14 days countdown or minus 14 days is the ovulation day. The ovulation day and the 5 days before and 4 days after the ovulation are called the ovulation period. This is the theoretical basis of the safe period contraceptive method.

　　For example, if a woman's menstrual cycle is 28 days, and the first day of this menstrual period is December 2, then the next menstrual period will be December 30 (December 2 plus 28 days), and then subtract 14 days from December 30, then December 16 is the day of ovulation. The ovulation day, 5 days before and 4 days after it, that is, December 11-20 is the ovulation period.

　　Except for the menstrual period and ovulation period, the rest of the time are safe periods. Using safe period contraception is easy to fail. Because some women sometimes healthy Circumstances, environmental changes and mood swings can delay or advance ovulation, so the ovulation period calculated based on the menstrual cycle is not accurate enough.

　　“"Safe period" can also lead to pregnancy!

　　The doctor said that one egg and one sperm When they meet in the fallopian tube, pregnancy occurs. During a typical 28-day menstrual cycle, female Generally, a mature egg is produced in the middle of the cycle, that is, between days 12 and 16. The ovaries excrete it into the abdominal cavity, where it is then sucked into the fallopian tubes, where it survives for about 24 hours. So only when sperm appears in the fallopian tube during this lucky period can a woman become pregnant. If the egg is not fertilized, the woman will have her period about 14 days after ovulation. During menstruation, another egg is developing in preparation for being released during the next cycle.

　　Not all women's menstrual cycles are the same length. Many people have a 28-day menstrual cycle, and some have a 22-day menstrual cycle. If your cycle is short, you may ovulate a few days after your period ends. Considering that sperm can survive in the fallopian tube for up to 3 days, it is theoretically possible that it could stay until a woman ovulates, allowing her to become pregnant within a short period of time late in her period.