Twins are the new black. With Beyoncé (and Jay-Z) and Amal Clooney (and George Clooney), announcing their impending bundles of joy, the world has gone gaga, especially with speculation about IVF.

Now, neither Beyoncé or Amal Clooney have confirmed they used IVF – but the former, 35, has gone on record saying the couple has been trying for a few years, and the latter is 39 years old, an age when popular assumption is that a naturally-occurring pregnancy is difficult to achieve.

Regardless, it got us wondering: Are the chances of twins with IVF really higher? Is it just a coincidence that all of these high-profile women in their mid-to-late 30’s are having twin pregnancy, or is it because they’re availing of medical fertility assistance?

How common are twins naturally? 

It really depends on which part of the world you live in. As of 2011, in India, and most of Asia, the twin birth rate is low – roughly 9 per 1000 babies. In Sub-Saharan Africa, it’s about double that.

But IVF isn’t widespread in either of those regions. So the best, educated guess comes from comparing the U.S.’s twin rate during the early days of IVF, when the procedure was uncommon, to today’s twin rate; per the country’s 2014 records, the rate of twin births was at 33.9 twins for every 1000 babies, or, an even 1 in 30 – which was a new high in the United States at the time. Data from 1980, when IVF was still not a household acronym, put the twin rate then at 1 in 53. So, there’s been a big increase.

How much did IVF play a part in that increase in twin births?

It’s impossible to determine, but common sense says it did play a role. Due to the cost of the procedure, and the advanced age of many women undergoing it, doctors frequently transfer multiple embryos into the womb to ensure a successful pregnancy – a sort of carpet-bombing approach to fertility. The assumption is, particularly with older women whose bodies are less able to carry pregnancies to full term, some of these fertilized embryos will not survive.

So, it’s likely IVF is responsible in part for the increase in multiples, simply because multiple embryos are being implanted, and — with today’s better medicine, nutrition and care — more of those embryos might be surviving past the initial stages of pregnancy.

That said, there are a host of other factors that increase a woman’s chances of twins with IVF — or without it, so the jumped-up twin rate in the US can’t, in good conscience, be pinned solely on IVF.

What natural factors increase a woman’s chances of twins with IVF or without?

Older mums (and medical science defines older as 35 and above) are more prone to having twins naturally; instead of one egg every cycle, women in this age group may release two or more. (Nature likes to carpet-bomb uteri, too.) And since women are waiting longer to have children, there are more older mums, and thus, more twins. (Older dads may also contribute to the incidence of twins – but the research is less clear on this.)

There’s a genetic component, too; research shows fraternal twins can run in families. (When it comes to identical twins, science is still stumped.)

So – what are the chances of twins with IVF?

If you’re undergoing IVF and implanting multiple embryos at a time, the chances of multiples with IVF increase — but, then, if you’re an older mum, your chances of multiples are higher anyway. So it’s a highly individualized roll of the dice, based on your health, age, genetic makeup, fertility and IVF procedure.

It’s not your imagination — twins are on the rise, but the exact cause of their increase is unclear — a cocktail of more advanced maternal age and more IVF procedures that we haven’t been able to parse.

In the meantime, we can look forward to a nice wave of #doubletrouble photos hitting our Insta feeds in about six months.