The number of twins born around the world each year has reached an all-time high.

A new study from Oxford University has found that, over the last 40 years, the number of twins being born has increased by a third.

The 1.6 million born every year equates to 12 pairs of twins per 1,000 births – up from nine in the 1980s.

The study suggests the rise is due to an increase in fertility treatments and more people deciding to put off having children.

Mikey O'Brien, Head of Nursing at Sims IVF, said women can react differently to treatments.

“The patients that have fertility treatments in the 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,” he said.

“But really, we would look at safety standards out there and we would look to the World Health Organisation which recommends, especially when it comes to IVF or ICSI, a single embryo transfer – which would mean one embryo transferred after treatment.”

At Dublin's Rotunda Hospital, 998 babies born in the last 6 years were twins, just under 2% of total births.

It peaked at 2.2% in 2017, with a low of 1.7% in 2019.

Mr O'Brien said people will occasionally look to have twins when going for treatment, but noted that twins can lead to a higher-risk pregnancy.

“We haven’t, to be honest, noticed an increase int eh number of twin pregnancies we would see,” he said.

“There is that notion out there that couples that do come through for IVF or fertility treatment are immediately going to have twins but that is not always the way because a twin pregnancy is a high-risk pregnancy and we definitely wouldn’t promote a high-risk pregnancy.”

The Oxford study found significant increases in twinning rate in many European countries as well as in North America; however, it notes that 80% of all twin are now born in Africa and Asia.

With reporting from Andrew Lowth