To determine the location of a point, we need to mark a coordinate original point.
In terms of pregnancy, theoretically, this origin is very clear, that is, the combination of essence eggs is the time of fertilization, that is, the starting point of pregnancy.
But the question is, how do we know the days of fertilization?
We know that mathematical coordinates are based on a certain reference system.
That is to say, in order to build a quantifiable coordinate system, you need to determine a reference with considerable certainty and showing.
Obviously, in this coordinate system during pregnancy, because fertilization does not have significant external characteristics that can be observed, we cannot determine the fertilization day, and we have to choose the observed reference event that can be observed in this coordinate system.(Time point) as a reference point.
In the women’s reproductive cycle, only the menstrual tide is the most observed event.
We know that because the reproductive performance of men is not periodic, this large amount of sperm is stored at all times in the epididymis and semen, and can be exhausted for fertilization through ejaculation at any time.
However, women’s reproductive properties have significant periodicness. Each cycle (average is 28 days) usually has only one egg that can develop and mature, and excrete it from the ovaries.
In this way, women’s ovulation actually determines the time when fertilization can be generated. This is why you need to choose sexual behavior as much as possible by calculating as much as possible.
In other words, the first thing that determines the reproductive cycle is the first to develop, grow, mature and ovulate in the ovarian.
That is, the ovarian cycle is the real core of the human reproductive cycle.
At the same time, if you want to conceive, the uterus also needs to prepare accordingly. As long as it is reflected in the periodic changes of the endometrium, after the ovulation period, the endometrium needs to become "fertile" and it is conducive to the fertilized egg or the fertilized egg orEmbinry of embryo.
However, not every reproductive cycle will be fertilized.On the contrary, most of the cycles will not be generated or embryo (whether it is natural or considers control).
Once there is no embryo implantation, the endometrium that becomes "fertile" has become a "waste expression". In the end, it needs to be "revoked" in time to make preparations for the next cycle.
The endometrium of "cancellation" will be excreted from the vagina through the vagina. This is menstruation.
The periodic changes of the above ovarian and endometrium are coordinated by the superior leader Xiaqiu brain-pituitary to release hormones and simultaneously.
In other words, the female reproductive cycle includes at least three aspects:
Ovarian periodic changes marked by ovulation;
The endometrium cyclical changes marked by vaginal bleeding (most of the cycle that are not fertilized);
And, the periodic changes of pituitary hormones as the initiator.
Obviously, if no continuous laboratory inspections are performed, we cannot just understand the changes in pituitary hormones through direct observation;
There are no obvious signs that can be observed directly to help us determine the changes and ovulation of the ovary;
Instead, a considerable amount of vaginal bleeding for a few days in a row is a significant external signs that cannot be ignored anyway.
Because of this, women’s reproductive cycles are called menstrual cycle.
In this way, the menstrual cycle represents the female physiological cycle or reproductive cycle, and on the first day of menstruation, in the basic problem, the "holiday start (first day)" is used as the origin of the menstrual coordinate system.
For the same reason, calculating the pregnancy time also had to "borrow" the menstrual tide as a reference, and the first day of the menstrual tide on the first day of the "benchmark" was used as the original point.
So, what is the relationship between the first day of menstruation and the real "origin" of pregnancy -what is the relationship between fertilization?
For women with a period of menstrual cycle and per surrounding, the first day of menstruation is about 14 days earlier than the fertilized date.
Conversely, the pregnancy time calculated on the first day of menstruation as the time of time to reduce 14 days is the actual pregnancy time.
However, due to the large difference in follicular periods in the ovarian cycle, the short ones are only 5 days, and the long ones are nearly 20 days.
Therefore, there may be a large error in this inference method.
The difference between the above two maximum time is the possible error generated by the first day of menstruation as the first day of pregnancy.
That is, up to 14 days.