The world is filling with twins: Number of Births Never Before

Demiagraphian Monden of Oxford University and his colleagues analyzed data from 165 countries from 1980 to 2015. The global birth rate of twins has increased by one-third since the 1980s -- from 9 per 1,000 births to 12 per 1,000 -- broadcast Telegrafi.

The largest growth was recorded in identical twins; that is, those developed by separate eggs. The birth rate of identical twins has remained approximately the same throughout these years.

Hormones stimulate issuing more eggs

“The biggest factor in rising twin births in high- and medium-income countries is the increased use of fertility treatments”, Monden said.

Women who receive hormones that stimulate egg production are more likely to release two eggs at the same time, writes Newe Scientist.

Artificial Ferconization and Later Family Formation

Also, in clinics performed by IVF, two, three, or more embryos are frequently placed in the womb to increase the chances of at least one surviving. This can lead to the development of twins, or threefold or fourfold.

Because babies are prone to higher health risks during pregnancy, such as premature or underweight, many health agencies now recommend that a single embryo be placed in the womb, meaning that there may be a decline in the birth rate of twins in the future.