It’s only been a little over a week since Beyoncé revealed that she would soon be Beytwice — and already another celebrity power couple has announced they’re expecting twins. While on a press tour for his white savior epic, Matt Damon confirmed the news that Amal and George Clooney will soon be the most “awesome parents,” suggesting that the trend of slightly older parents having multiple births is going strong.

Amal, 39, and George, 55, are not only joining the multiple-birth celebrity club (membership also includes Pharrell Williams) but also the ranks of older parents, famous or not, who are giving birth to twins. This distinction is important because it might very well be why they are having twins in the first place. Studies demonstrate that older women have more difficulty conceiving compared to younger women but are also more likely to have twins when they do.

When women are between the ages of 38 and 48, their bodies produce a larger amount of follicle stimulating hormone, the chemical that kickstarts the maturation process of immature eggs. In the body, each pre-egg, known as an oocyte, lives inside an ovarian follicle, which is a fluid-filled sac (one of many) in the ovaries. Typically, only one follicle becomes a part of a woman’s monthly ovulation cycle; the rest are absorbed by the ovaries. But because older women produce more follicle stimulating hormone, it increases the chance that a simultaneous double ovulation will take place, assuming the eggs are healthy. When there are two eggs in ovulation, there’s a greater chance that, if they are successfully fertilized by sperm, a woman will become pregnant with twins.

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The ovaries and their follicles.
An artist's representation of an ovary.

The way an older woman’s body naturally works and in vitro fertilization (IVF) treatment are similar in the sense that they both involve multiple fertilized eggs, now embryos, making their way into a woman’s uterus. Women using IVF sometimes choose to implant multiple embryos into the uterus in order to increase their chance of becoming pregnant, but sometimes this means that these multiple embryos will turn into multiple babies. IVF results in twins 20 to 30 percent of the time.

A pair of baby twins.
Will the Clooney twins wear matching hats?

It’s not just celebrities who are having a surge of twins — the twin birth rate in the United States is at an all-time high. The CDC reports that 33.9 per 1,000 births in 2014 were twins, which some researchers credit to older mothers either becoming pregnant to twins naturally or because they had an IVF treatment. We can’t speculate which was the case for Amal (nor should we), but her incoming brood will enter a nation in which being a twin is fast becoming the new normal.

Photos via Wikipedia Commons, Pixabay, Getty Images / Clemens Bilan