The study concludes that treatments such as IVF have led to the significant rise in the number of twins being born around the world.

A worldwide study by Oxford University researchers has found the number of twins being born has increased by around a third in 40 years.
The researchers believe the rate of twin births is now at an all-time high.
The study shows more than 1,600,000 twins are being born every year, and concludes that treatments such as IVF have led to the so-called 'twin peak' globally.
Mikey O'Brien, who is Head of Nursing at Sims IVF, has been commenting on the study:
"Patients that have fertility treatments that are in a younger age bracket, maybe in their early thirties, they might be more susceptible to twins because they might respond to medications in a different way."
Among some high profile twins in Ireland are Jedward, as well as Taoiseach Micheál Martin, who has a twin brother named Padraig.