Does the Chinese pregnancy chart work?


The Chinese pregnancy chart, also known as the Chinese baby sex chart, is a technique developed by traditional Chinese medicine, which is supposed to have the ability to predict the sex of the baby based on the Chinese lunar calendar.

The Chinese table has become very popular on the Internet, and there are hundreds of websites that indicate this technique for pregnant women who are curious to know the sex of their baby. There are also those who recommend the chart for couples who have not yet become pregnant, but want to be able to choose the sex of their future child. Supporters of the Chinese table say that the technique is more than 90% effective. Some sites go further and claim that the table’s efficiency is 99%.

But what does science have to say about the Chinese table? Are there any scientific studies about this method? If the Chinese pregnancy chart is just a folklore, a myth, why has it become so popular on the Internet?

In this article we will talk specifically about the Chinese table; if you are looking for information about scientifically proven ways to know the sex of the baby during pregnancy, read the following article: How to know the sex of the baby – Is it a boy or a girl?

What is the Chinese pregnancy chart?

Chinese pregnancy chart

According to legend, the Chinese pregnancy chart was used by the emperors as a guide so that they could choose the sex of their future children, thus ensuring that they would have male descendants, which assured the continuity of their royal lineage.

Below we provide an example of the Chinese table, as published annually by the Chinese Farmers’ Almanac. To use the Chinese table, it is necessary to use some tools, which serve to equate the Chinese calendar with our Western Gregorian calendar. These tools are easily found on the Internet. This table was not designed to be used with our traditional calendar (I will explain some differences between calendars later).

Depending on the source in which one researches, the history of the Chinese table usually presents some important differences. There are at least three distinct versions for the origin of the table:

  1. The most elaborate version of the story says that the Chinese table for predicting the sex of the baby is a chart that originated in the Qing Dynasty (1644-1912) and disappeared in 1900 in the Summer Palace of Emperor Guangxu after the Dynasty lost the war with the Eight-Nation Alliance in the same year. At the end of the confrontation, the original table would have been sent to England where the British monarchy kept it hidden as treasure. Many years later, in 1972, under unclear circumstances, the paper turned up in Austria. There it was seen by a Chinese historian, who copied the contents and published it in a Taiwanese newspaper. Since then, the chart has been published annually by the Chinese Farmers’ Almanac and is available in the delivery rooms of Chinese hospitals.
  2. Another version about the origin of the chart says that the chart was found near Beijing in a Qing Dynasty royal family tomb. The chart would be about 700 years old, thus predating the Qing Dynasty.
  3. A third version tells that the original Chinese chart was found in an underground room of the Forbidden City in the Qing Dynasty. The chart would have been conceived from the theory of Yin Yang, the 5 elements (metal, water, wood, fire, and earth), and Pa Kua.
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Despite the different stories about its origin, all sources agree that the chart is based on the Chinese age of the mother and the month of conception, always according to the Chinese lunar calendar, which entails some relevant differences when compared to our Western Gregorian calendar, which is based only on the sun.

According to some sources, in China a baby is born at the age of 1 and turns 2 years old on the day of the Chinese New Year, which is usually between January and February, with no fixed annual date.

Therefore, in order to use the Chinese table, one must first find out how old the mother is according to the Chinese calendar. In general, except for women who were born in January and February, the Chinese lunar age is one year higher than the actual age.

For example, if you were born on 30.08.1990 and became pregnant on 20.09.2016, your actual age will be 26, but your Chinese age will be 27. On the other hand, if you were born on 25.01.1990 and became pregnant on 20.09.2016, your actual age and your Chinese age will be 26.

Problems of the Table

In light of current scientific knowledge, there are numerous theoretical problems with the Chinese table; and none of the sources explain what the relationship or logic is behind using the mother’s age and month of conception in defining the sex of the baby.

What would be the rational explanation for us to believe, for example, that all women in their 30s who were fertilized in the month of June will always have male babies? And what is the reason why 21-year-old women only have a chance of having male children if conception occurs in the month of January?

When this kind of prediction, which escapes common sense and fights with the law of probability, is made, we expect a good explanation to be provided, otherwise the use of the table is much closer to superstition than to rationality.

But the problems with the foundations of the Chinese table do not boil down to a simple lack of logical explanations of how it works. There are widely known issues that make the reliability of the table low. Let’s mention a few of them:

  1. The first problem is knowing exactly the day of conception. We know that conception in most cases does not occur on the day of sexual intercourse. Sperm can survive for up to 5 or 6 days inside the female reproductive tract. Therefore, a woman who had intercourse on April 29 may have ovulated (and been fertilized) only on May 4. This implies that all women who had intercourse in the last week of the month will have a hard time telling when it was actually the month of their conception (we explain the fertile period in more detail in the article: What is the most fertile period to get pregnant?).
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What about women who have had multiple relationships in the last few months? How to know the correct day of conception?

  1. We know that who “defines” the sex of the baby is the male sperm, which can carry the sex chromosome X or Y. If the sperm that fertilizes the egg has the Y chromosome, the fetus will be male; if it has the X chromosome, the fetus will be female. In defining the sex of the baby, the genetics of the woman has little or no influence, because since her pair of chromosomes are obligatorily XX, she can only donate an X chromosome to her child.

So it is strange that the Chinese table only takes into account the age of the mother and the month of conception. How could this data decide which type of sperm will be responsible for fertilization?

It is not impossible that the woman’s organism has some influence on the sperm choice, but for this to have any credibility, some plausible explanation is needed, preferably based on scientific data.

It is interesting to remember that the table was supposedly conceived several centuries ago, at a time when scientific knowledge was very poor. It makes perfect sense that the ancient people imagined that somehow it was the woman’s organism that decided the sex of the baby.

  1. How to explain the cases of women who have twins, each one of a different sex?
  2. If the table is really effective, how to explain that the line of succession of Chinese emperors is not composed exclusively of male children throughout history?

What do the scientific studies say?

Many websites that make the case for the Chinese table often describe the chart in the following way: “although there is no scientific proof, the table has an impressive accuracy rate”.

In fact, there is scientific proof. The problem is that studies show exactly the opposite, that the table is not reliable and has a low hit rate. Therefore, the scientific consensus is that the table is not reliable.

The most famous and important study about the Chinese table was done in Sweden in 2010 (sources at the end of the article).

In this study, the researchers collected data from about 3.4 million births that occurred between the years 1973 and 2006. Of these, the researchers were able to obtain reliable data from the mothers in about 2.8 million cases.

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The hit rate for the Chinese table in this group of 2.8 million women was about 50 percent, i.e. exactly the expected rate of effectiveness for any test that does not work, such as trying to guess the sex of the baby by tossing a coin. And the rate was always around 50%, regardless of the mother’s age or the month of conception.

This Swedish study is the largest, but not the only one. There are several studies published on the effect of the lunar calendar on pregnancy, not only on the sex of the baby, but also on the delivery date, risk of complications, the baby’s development, and increased fertility. In all of them, no causal relationship between the lunar calendar and pregnancy outcomes could be proven.

Why is the Chinese table so popular on the Internet?

The Chinese table has a 50% accuracy rate. This means that out of 3 million pregnant women, it will get the sex of the baby right for 1.5 million. So even with a high error rate, for 50% of the people who take the test, it will appear to be effective. The chance that the test will get the sex right with 2 children is 25%, or 750,000 women in a universe of 3 million pregnant women. That is why it is so common to find reports from mothers who assure that the table is really reliable.

Conclusion: the Chinese table is not reliable

From everything explained so far, as expected, we can conclude that the Chinese table for predicting the sex of the baby has no plausible theoretical basis and has failed to be scientifically tested on a huge group of women.

And it is not only the gender of the baby that the chart gets wrong. So far, all studies trying to find some relationship between the moon phases and pregnancy outcomes, be it delivery date, risk of complications, baby’s health, etc. have failed. have not been successful.

If you are pregnant and want to know the sex of your baby, the most reliable ways are the fetal sex test, which from the 8th week of gestation has more than 99% accuracy rate, or through fetal ultrasound, which from the 14th week of gestation can already identify the baby’s genitalia.

Just as a personal note, the author of this text has three daughters. The Chinese table got the sex wrong in two of them.