A new study suggests the number of twins born worldwide is rising. The reason for this seems to be the rising use of in vitro fertilisation (IVF) and other assisted reproduction techniques.
Back in the 1980s, each year would see the birth of around 1.2 million twins. Now, that number has risen by a third to 1.6 million. However, the authors of the study think we are now at the peak. In wealthier regions such as Europe and the US fertility treatments aim to minimise multiple births.
Professor Christiaan Monden, Oxford University, UK led the study. He said, “We think we’re actually at the peak. This is likely to be an all-time high. The relative and absolute numbers of twins in the world are higher than they have ever been since the mid-twentieth century.”
He and his team analysed data on twin birth rates for 165 countries from 2010 to 2015. They compared this data with data from the 1980s.They found a 71% rise in twin births in the US. There were also significant rises in many European countries. In Asia there was a 32% increase.
Interestingly there were differences in the number of types of twins being born. The number of identical twins has remained the same at about four per thousand during this period. So, it is the non-identical twins, twins that are conceived from separate eggs, that have seen an increase.
The reason for this is thought to be genetic. For instance, in Japan most twins are identical, whereas in Africa most twins are non-identical.
Professor Monden concluded that:
- women choosing to start families later
- greater use of contraception
- lower fertility rates
- IVF
All play a part in the increase in twin births. But reproduction techniques like IVF, which began in the 1970s are the main drivers.
