It turns out that the 'probability of having twins' is increasing all over the world, and why?



A research team consisting of researchers from Oxford University and the French National Institute of Demography surveyed the 'ratio of twins born' around the world, and found that the proportion of twins born has increased compared to 30 years ago. It turned out.

Twin Peaks: more twinning in humans than ever before | Human Reproduction | Oxford Academic
https://academic.oup.com/humrep/advance-article/doi/10.1093/humrep/deab029/6168658



More Twins Are Being Born Today Than Ever Before in History. Here's Why

https://www.sciencealert.com/more-twins-are-being-born-now-than-ever-in-history-here-s-what-could-be-happening

The research team collected demographic data from 165 countries from 2010 to 2015 to investigate the proportion of twins born. As a result, it was found that from 2010 to 2015, 12 out of 1000 births were born. In addition, a similar survey conducted from 1980 to 1985 recorded that out of 1000 births, 9.1 twins were born. From this, the research team claims that 'the proportion of twins born is increasing.'

The following is a world map created by the research team that shows the 'ratio of twins born in each country'. The countries surveyed are filled with darker colors as the proportion of twins born increases. If you look at the world map, you can see that the proportion of twins born is particularly high in Africa and North America.



The research team also calculated changes in the proportion of twins born from the 1980-1985 survey results and the 2010-2015 survey results. In the world map below, countries with increased twin birth rates are painted green and countries with decreased twin births are painted blue. If you look at the world map, you can see that in many countries in North America, Europe and Oceania, the proportion of twins born is increasing, and in South America, Africa and Asia, it is decreasing in some countries.



The graph below shows the changes in the number of births (blue), the number of twin births (red), and the proportion of twins born (green) during both the '1980-1985' and '2010-2015' periods for each region. Shown in. If you look at the graph, you can see that in Europe, South America and Asia, the number of births is decreasing, but the proportion of twins is increasing. In North America, Oceania, and Africa, the number of births and the proportion of twins born increased. In addition, if you look at the global average, you can see that the proportion of twins born is increasing.



The research team pointed out that 'more people are using medical reproductive support technologies such as in vitro fertilization' is the reason for the increase in the proportion of twins born all over the world. Generally, when in vitro fertilization is performed, multiple embryos are fertilized in order to maximize the probability of success. Therefore, it is easier for twins to be born.

In addition, the research team cites 'late marriage' as another factor. Another study , published in 2018, found that white women were three times more likely to have dizygotic twins and black women were four times more likely to have dizygotic twins when they gave birth over the age of 35.

in Science, Posted by log1o_hf