Fetal sex fortune telling _ Is it accurate?

Male and female numerical algorithms for predicting the next child from one child.

Shi Zhuang Lihe

doctor

Senior medical consultant of Santino

Master of Neuroscience, Hokkaido University

In ancient China, fortune tellers often helped to decide whether to have a boy or a girl, and directly put up a sign: "No money!" !

And the quotations of these fortune tellers are often very expensive, ranging from hundreds to tens of thousands.

For example, if you predict that you will have a boy, you will receive 8000 yuan. If your prediction is successful, the whole family will be very happy. You may boast that Teacher Zhi is a contemporary Yuan Tiangang, a near-re-embodiment millet, and even give him a big red envelope.

Moreover, the prediction was wrong. Some people thought about it and repeatedly chanted the slogan of family planning propaganda: boys and girls are the same, and daughters are more filial to their parents; Some ungrateful people want to ask Mr. Wang for a refund, but they didn't expect to give Mr. Wang a scolding-this is God's will, how can it be artificial!

As a new era medical student who has been studying biochemistry since high school, he can certainly see through the fortune teller's tricks at a glance: the probability of giving birth to boys and girls is obviously 1: 1. Suppose 100 fortune tellers come to tell fortune, half of them are boys and half are girls, and all fortune tellers bet on men. In the end, it's a profitable business for men to earn money and women to refund their money!

Today, however, I want to tell you a serious fact:

The probability of boys and girls is a misunderstanding. Under natural conditions, the birth probability of boys is higher than that of girls.

As shown below, this is the ratio of male to female newborns in OECD countries.

Why are there so many treasures?

Scientists had a long and heated debate on this issue.

Kettel's theory

1960, an American biologist named Lan Drum Kettel first put forward a conjecture.

We know that at the moment when X-carrying or Y-carrying (hereinafter referred to as X or Y) is combined, the sex of the baby has been determined.

So, is it because y is easier to combine?

Y is smaller than X, so Y is light. The smaller the weight, the faster it runs, so Y swims faster and can be combined earlier.

According to this theory, Shettles and his friends later created a theory called Shettles to help parents choose the sex of their children.

According to this theory, Y runs fast, has a short life span and is easily influenced by acidity, so the closer the insemination time is to ovulation time, or the closer it will be to the mouth (where the acidity is less than outside), the greater the possibility of having a boy; If you want a girl, do the opposite.

Kettel's theory is widely spread. The "Millennium Ancestral Art" circulating in China today, as well as the theoretical viewpoints in many health-preserving bestsellers, and even the acidic physique theory with a very broad mass base in the circle of friends are actually influenced by Kettel's theory to some extent.

Kettel's theory is

However, many doctors and scientists in the United States don't believe Kettel's theory.

From 65438 to 0995, American epidemiologist james wilcox studied 22/kloc-0 women for a long time, recorded more than 600 ovulation cycles, and recorded the date and date of their couple in detail.

The results show that almost all pregnancies are due to the time difference between the first six days and the last six days, regardless of the sex of the baby.

This study was later published in NEJM (New England Medicine), which is also the rigorous theory of Shettles.

That's not enough. With the rapid development of computer technology, in 1998, researchers used computer-aided analysis technology (CASA) to observe the movement more accurately.

The results show that although X carries more DNA than Y, Y and X have the same moving speed. The only difference is that their movements are different in linearity.

Moreover, there is no difference in the ability to combine the two. In fact, at the beginning of life, the ratio of male to female is extremely close to 1: 1.

Then the question is, why are there more babies at birth than girls when the ratio of men to women is the same?

Where did the baby girl go?

In the past, academic circles always thought that men were more vulnerable than women from a physiological point of view.

For example, the average life expectancy of men is lower than that of women. You are like China with the longest life expectancy in the world (yes, it has surpassed Japanese). The average life expectancy of men is 865,438+0 years, and that of women is as high as 87 years.

For another example, the incidence of almost every kind of cancer is higher in men than in women; Some cancers may differ by only a few percentage points, while the incidence of some cancers in men is even 2-3 times higher than that in women.

However, before birth, things may be different.

In 2022, the team of American biologist Steven Orzack conducted a larger and most comprehensive study on the sex ratio of the fetus at birth.

Contrary to popular belief, female fetuses are actually more fragile.

It is found that the mortality rate of male and female fetuses is constantly changing at different stages.

At present, the proportion of male embryos is the same as that of female embryos;

In the first two weeks, the mortality rate of male embryos was high, and the male ratio began to be lower than 0.5;

After 10 ~ 15 weeks, the fetal mortality rate of women was higher than that of men, and the proportion of men increased by more than 0.5. This trend continued until the 20th week.

After 28 ~ 35 weeks, the male fetal mortality rate rose again, and the male ratio began to fall back until it was close to 0.5, but it would not be lower than 0.5.

Different from what many of our previous textbooks said, this study with a sample size of nearly one million found that there is almost no trend in the primary sex ratio of human beings. Throughout pregnancy, the mortality rate of female fetus is higher than that of male fetus.

The specific reason is still unclear. The only thing we know at present is that it may be related to NO. 15,No. 17 and. This alternate change in fetal mortality eventually leads to more babies when they come out of the uterus.

This study was later published in PNAS. This study has studied some inherent viewpoints in textbooks, and the far-reaching significance of this study is that it shows that even with the development of medicine today, we may still have some wrong understandings of those things of human beings.

Whether it is determined by human genes or arranged by nature, under the influence of various coincidences, most of them are born with slightly more boys.

However, because men are adventurous and aggressive, and men are more susceptible to some diseases, by the age of 20, the mortality rate of men is higher than that of women, which can be regarded as a side manifestation of the balance of nature.

Zhihu ID: Zhuang You Mao

Master, Hokkaido University, Japan

Editor Bruce

Shi Zhuang Lihe

The typesetter smiled.

The above is the content of calculating the number of men and women who predict the next child with the previous child, and it is about the sharing of fortune tellers. It's so accurate after reading it! After seeing men and women, I hope this will help everyone!