More twins are being born than ever around the world, according to a large demographic survey. Twins are born in one in 42 births.
The study, published today in the journal Human Reproduction, was done in 165 countries. In recent years, around 1.6 million twins have been born worldwide every year, the inventory showed. Since the 1980s, the percentage of twins has increased by a third, from 9 to 12 in every 1,000 births.
The researchers think that this may have reached a peak in the number of twin births. In a number of countries the percentage of twins is no longer rising, in some countries it is even decreasing.
Artificial insemination
Researchers compared the figures for twin births by country in the period 2010-2015 with those for the period from 1980 to 1985. Today, a lot of twins are born in Europe and North America. This is mainly due to the more frequent use of techniques such as IVF, ICSI, artificial insemination and ovarian stimulation. All these techniques increase the chance of twins.
But relatively many twins are also born in Africa, and that has not changed in thirty years, researchers found. There is an explanation for this, says sociologist Christaan Monden, one of the researchers, to the BBC. “In Africa, the number of fraternal twins is high. This is probably due to genetic differences between the African population and other populations.”
As population growth has increased, the number of twins in Africa and Asia is on the rise. In those continents, 80 percent of all twins are now born. Only in South America, in absolute numbers, no increase can be seen.
Mortality
The study also found that the situation of twins is worrisome in countries with low or average per capita income. In many African countries, children lose their twin siblings in the first year of life, according to an earlier study in 2017.
Jeroen Smits, professor of Economic and Human Development at Radboud University, participated in both studies. According to him, the information collected is of great importance. “The death rates of twins in these countries are still very high. Particularly in Sub-Saharan Africa, many twins lose their twin siblings in their first years of life. That’s about three hundred thousand a year.”
In the coming years, the number of twin births in India and China, where 36 percent of the world’s population lives, will determine whether the number of twins worldwide continues to rise or fall, the researchers think.
–
