Paris.- Not many twins have been born in the world, a phenomenon due to the prevalence of medically assisted childbearing and late gestational ageThis Friday, a group of investigators confirms.
more than 1.6 million twins are born every year In the world, that is “One in 40 childrenAccording to the study published in the specialized journal Human Reproduction.In this file photo taken on August 11, 2018, twins and triplets are seated in their stroller as they arrive at the Twins Children’s Festival in Kiev.Sergey Supinsky – Agence France-Presse
Since the 1980s, the global twin birth rate has increased by a third, from 9.1 to 12 per 1,000 birthsIt’s only three decades in, says Gilles Besson, a professor at the National Museum of Natural History and associate researcher at the National Institute for Demographic Studies (INED), based in France.
This double boom is of concern because they are often born under the correct weight, are premature, have more complications during childbirth and suffer more deaths than others. This goes beyond the difficulties that parents have to take care of two children at the same time.
The increase in the frequency of twins worldwide is only due to the unprecedented increase in the number of twins Carry what are known as “false twins” (from two different eggs), which vary between continents and from one period to the next.
Real (monozygotic) twins are born everywhere in the same proportions, with a “constant rate – four births from original twins per 1,000 births – that does not differ according to the woman’s age, nor between regions,” Besson notes.In this file photo taken on August 5, 2017, Noah and Owen Goree, 20 months old in Cleveland, sit in the shade during the forty-second annual Twinsburg Festival in Twinsburg, Ohio.Dustin Franz – French Press Agency
The Medical assisted reproduction, which began in wealthy countries in the 1970s, has contributed to this increase in multiple births, Such as late pregnancies.
The level of the hormone involved in egg maturation and ovulation in the blood, FSH, increases with age and increases the likelihood of having twins, and reaches its peak at the age of 37. From this age (if medically assisted reproduction is not used), the rate of false twins drops rapidly Due to failure of ovarian function and increased fetal mortality, the researcher explains.
Technical advances in assisted reproduction have made it possible for years of pregnancy to be successful by implanting one embryo and freezing the remaining embryos. This means that we “may have reached a peak in terms of twin rates, especially in rich countries,” the authors say.
The study authors, Jill Besson and Christian Mundin of the University of Oxford, and Jeroen Smits of the University of Radboud in the Netherlands, used all available data to estimate the rate of twins in different countries and describe changes over three decades, comparing the periods 1980-1985 and 2010-2015.
Of the 3.2 million twins born each year, 1.3 million are born in Africa (650,000 pairs), many of them in Asia. The rest, about 600,000 children, are on other continents.
If Asia has a lot of twins, it is mainly because it is home to 60% of humanity.
The large number of twins in Africa (17%) is due to a much higher birth rate than anywhere else And because after that there is actually the highest rate of twins in the world.
even in Africa, the rate is 17.1 twins per 1,000While in South America it is 9.3 for the 2010-2015 period, and in Asia it is 9.2.
The twin birth rate in Europe and North America 30 years ago was almost half that of Africa, but increased sharply (reaching 14.4 and 16.9 twin births per 1.