More twins are being born than ever. Every year they are born into the world more than 1.6 million pairs of twins, according a study published in the specialized journal Human Reproduction, one of the most important reproductive medicine journals in the world.
Since the 1980s, the twin birth rate has increased by a third, from 9 to 12 per 1,000 deliveries, meaning that one in 42 babies is a twin. However, this increase has only been observed with fraternal twins, coming from two different ovules, which we know as twins; while the birth rate of identical twins, known as monozygotes, remains the same.
The study finds that one of the main causes of this increase is the growth of medically assisted reproduction, which includes not only IVF techniques (fertilization in vitro), but also simpler methods such as ovarian stimulation and artificial insemination.
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Another cause of the increase is the delay in childbearing observed in many countries during the last decades, since the probability of having twins increases with the age of the mother.
A peak in births, expected to decline
The researchers analyzed birth records between 2010-2015 and 1980-1985 in more than 100 countries and found a significant increase in twin birth rates in the past 40 years.
However, researchers think we may have peaked in these births, particularly in high-income countries like Europe and North America, due to the growing emphasis on the importance of trying to achieve singleton pregnancies.
Professor Christiaan Monden of the University of Oxford (UK), the first author of the study, said:
“The relative and absolute number of twins in the world is higher than ever since the mid-20th century and this is likely to be an all-time high. This is important as twin deliveries are associated with higher death rates among infants. and children and further complications for mothers and children during pregnancy, and during and after childbirth. “
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Twins in the world
Twin rate per 1000 births between 2010 and 2015
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Of the 3.2 million twins born each year, 1.3 million are born in Africa (650,000 couples) and the same number in Asia. The rest, about 600,000 children, in the rest of the continents.
That Asia has so many twin births is because it brings together 60 percent of humanity. The large number of twins in Africa (17 percent of humanity) can be explained in particular by a much higher birth rate than elsewhere, which is between double and triple that on other continents.
The twin rate in Europe and North America 30 years ago was almost half that of Africa, but has increased significantly since then (reaching 14.4 and 16.9 twin deliveries per 1,000, respectively) and has almost reached that of Africa, which has barely changed (17.1).
In Babies and more | Babies born using assisted reproductive techniques already account for 9% of all births in our country
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