What do you mean by the first three and the last four?

The first three and the last four have the following two meanings:

First of all, the dictionary is interpreted as:

1, Sui, Tang and Song customs, with winter solstice, Jacky and cold food as the main festivals, have seven days off, including three days before the festival and four days after the festival, commonly known as "the first three and then four";

2, Song, Wang Xun' Wild Guest Series Seven-Day Holiday':' State officials and private, to winter, cold food for seven days off, the so-called first three after four. The servant has tested it, and it is still coming. "

Second, the female safety period

1, people simply summarize it as the first three and the last four, and some people say that the first seven and the last eight (often mentioned in Hong Kong and Taiwan films), but these are not accurate, in fact, they should vary from person to person;

2. Usually, the ovulation day of women is before menstruation 14 days. Considering the survival time and error of sperm in women, the first 5 days to the last 4 days of ovulation day are generally called "dangerous period". During this period, it is more likely to get pregnant in the same room, and other times become a "safe period", so it is less likely to get pregnant.

3. In addition, it is obvious that the safety factor of the "safety period" after the "dangerous period" is greater;

4. The safety period algorithm also has some limitations. For example, some women with irregular menstruation are not suitable for safe period contraception;

In addition, women also have irregular ovulation caused by emotional changes.