More twins – almost one in 40 children – are born than ever before, according to research published on Friday, citing the rapid increase in medically assisted reproduction as a major factor.
More than 1.6 million twins are now born each year, say researchers in an article published in the scientific journal Human Reproduction.
“The relative and absolute number of twins in the world is higher than they have ever been since the middle of the 20th century and this is likely to be a record high,” said Christiaan Monden, University of Oxford (UK), said one of the study’s authors. .
The increase in assisted reproduction technology (ART) in developed countries since the 1970s contributed to the increase in the number of births, they said, as well as mothers giving birth at an older age, when the frequency of friendships is higher.
Increased use of contraception, women who chose to start families later in life and lower total fertility were also responsible.
Researchers collected data from 135 countries from 2010-2015 for the study.
The proportion of twins was highest in Africa, they said, citing “genetic differences” between the continent and the rest of the world.
The increasing number of twins in poorer parts of the world was worrying, said one of the researchers.
“Twin deliveries are associated with higher death rates among infants and children and more complications for mothers and children during pregnancy … during and after childbirth,” Monden said.
“More attention needs to be paid to the fate of twins in low-income and middle-income countries,” says co-author Jeroen Smits.
“Especially in sub-Saharan Africa, many twins will lose their twin during their first year of life, about two to three hundred thousand each year, according to our previous research.”
Researchers said that the record number is driven solely by the births of “fraternal twins” – which are derived from two separate fertilized eggs.
The number of identical twins – so-called monozygotes – remained the same.