Why does September 23 correspond to the peak of births of the year?

• The date of September 23 is the day of the year when the most births are recorded in France.

• This trend was also the subject of a report published in 2011 by INED, according to which, "given the average duration of gestation (265 days), this peak [of births] corresponds to conceptions of New Year ".

  But this period has not always been the most popular.

• Why do so many French women give birth during this period?

  According to sociologists, this seasonality is due to the social upheavals of our society over the past decade.

Edit of September 23, 2022: As every year, we offer you the rereading of this article which explains this "boom" of births every September 23.

What do Julio Iglesias, Cyril Hanouna and Bruce Springsteen have in common?

They were all born on September 23.

Failing to wish them a happy birthday,

took an interest in a phenomenon noted for a decade in France: September 23 is the day of the year when there are the most births.

According to an INED report, entitled "Is there a season for having children", on average 5% more babies are born on this day than on other days of the year.

"Given the average length of gestation (265 days), this peak corresponds to New Year's conceptions", notes the Institute, which explains that "the conceptions giving rise to a live birth are almost twice as numerous" the night of December 31 to January 1.

At each era its peak

How to explain this peak of births?

“He has always been present,” notes Bénédicte Champenois-Rousseau, sociologist, specialist in births, science and technology.

“It's quite funny because it varies according to the times”.

Today, “the Christmas and January 1 vacation period [nicknamed the confectioners’ truce] is particularly favorable because we are on vacation and more often together,” she says.

In addition, "the end-of-year celebrations undoubtedly represent a period of" fragility "", judge the co-authors of the INED study, Arnaud Régnier-Loilier and Jean-Marc Rohrbasser: forgetfulness of pill, delays in its intake, episodes of vomiting which may be more frequent, alcoholism… There are also “more spontaneous and unwanted conceptions” therefore more requests for abortion during this period, notes Bénédicte Champenois-Rousseau.

But factors other than the lesser contraceptive vigilance explain this surplus of births.

Procreation according to the economy of the country

"Birth is not only a biological event, but also an event determined by social conditions", summarizes Bénédicte Champenois-Rousseau.

In Catholic France of the 17th and 18th centuries, sexual relations being prohibited during the periods of Lent and Advent, the peak of births was between January and April.

Moreover, “marriage was an important marker.

There were very few births outside marriage,” explains Stéphanie Toutain, sociologist-demographer, lecturer at Paris Descartes University.

And the ceremonies usually took place in late spring and early summer.

In the 20th century, the trend evolved, observe the two sociologists.

In 1936 comes the blessed time of paid holidays, so most couples find themselves on vacation in July or August.

"In the worker category, it's more the month of August," says Stéphanie Toutain.

With these conceptions during the summer, the peak of births gradually moved to spring (April-May).

Social changes have continued in recent years with the 35-hour reform, paid leave extended to five weeks spread over the year, but also a decline in appetite for marriage and its respect as an institution, the multiplicity of means of contraception and the lesser observance of religious precepts.

“Before, in a class of 30 students, you had a lot of children who had their birthdays around April-May.

Which corresponded to the conceptions of the month of August.

And now, there are more in September, ”illustrates Stéphanie Toutain.

"The seasonality of births would thus be 'determined' by the seasonal rhythm of the country's economic life", analyzes INED in its report.

A baby wanted but not conceived at the desired time

However, "a significant number of New Year's designs, even if they are not programmed, are desired", notes INED.

When French women are asked which month they would prefer to give birth, May is by far the most cited month (27%), ahead of June (20%), April (19%) and March (9%). , while that of September is mentioned by 2% of women, detail the researchers of the Institute.

“Most couples plan a birth in the spring because it's more pleasant for the mother and the newborn: the weather is starting to get warmer again and the days are getting longer.

A pregnancy that ends in the middle of summer is sometimes quite painful,” develops Bénédicte Champenois-Rousseau.

For French women who benefit from summer vacation [in National Education, for example], a baby who would see the light of day in April is also an opportunity to spend as much time as possible by their side [maternity leave + summer holidays].

But to aim for sunny days, "you have to stop contraception just before summer and since the body is not a machine...", adds the sociologist.

Indeed, a pregnancy does not materialize in the first month after stopping contraception.

You have to wait several months at times for the design to take effect.

This delay could be one of the reasons why births are more numerous in the fall and not in the spring.

A future effect of the climate?

This peak in births has no impact on the annual demographic average.

According to the latest INSEE census (published in December 2018), France – excluding Mayotte – had 66.36 million inhabitants on January 1, 2016, “i.e. growth of 0.4% per year since 2011”.

France is a country where the birth rate is dynamic [more than its European neighbors] with 1.88 children per woman.

However, the fertility rate has been falling for three years.

In 2016, there were 1.92 children per woman in 2016 and two children in 2014.

And if winter and its chilly temperatures, conducive to nights under the duvet, became shorter with climate change, could we expect new fluctuations in the seasonality of births?

“That's an interesting question.

But I don't think there are any answers to prove this theory.

What studies show today is that it is more social constraints that will affect fertility than physical constraints,” replies Bénédicte Champenois-Rousseau.

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France has nearly 67 million inhabitants on January 1, a figure up by 0.3%

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