Why Are so Many Celebrities Having Twins?

I've never really followed the celebrity baby boom, but it's near impossible not to see the constant updates about Knox and Vivienne Jolie-Pitt. I'm actually relieved they're finally born so we can stop getting constant coverage over their impending births.

Of course now we get to see how much their baby photos will fetch and if they indeed are the most beautiful twins on earth. (Move over Mary-Kate and Ashley Olsen). However, with all this Jolie-Pitt twin hysteria, I've noticed an inordinate amount of celebrities are having twins lately.

Celebrities with Twins

Angelina Jolie and Brad Pitt
Knox and Vivienne

Julia Roberts and Danny Moder
Hazel and Phinneas

Jennifer Lopez and Marc Anthony
Max and Emme

Rebecca Romijn and Jerry O'Connell
Expecting in 2009

Marcia Cross and Tom Mahoney
Savannah and Eden

But is it just a new Hollywood fad, the result of modern science, or just Mother Nature at work? My guess it's a combination of the latter. Older women are known to release more than one egg during their menstrual cycle and show elevated hormones. Their biological clock essentially speeds up in their 30's. And as society standards have shifted and more and more women are waiting until their 30's and even 40's to conceive, the number of multiple births has skyrocketed. Specifically, the number of twin births increased by 66% between 1980 and 2003.

Additionally, some women put off pregnancy for so long their eggs become sluggish or are no longer viable without the nudge of modern science. More women turn to In Vitro Fertilization which boosts hormone levels and speeds up fertility. This can also lead to multiple births including twins, triplets, and beyond.

Despite the fact that it's some parents' nightmare to find out their having twins -- twice the trouble -- others are vying for an opportunity for multiples. It's an opportunity to double their family size without a long road of multiple pregnancies ahead. Others may have experienced difficulty getting pregnant and wish to speed up the process or avoid another round of waiting and disappointment. So what are the odds of having twins? Statistically, the odds of having a twin birth are 1 in 33, or 3%. But are there ways to increase your chances of multiples?

Factors that will increase your odds of having twins:

*Your chances of having twins increases from 3% to 4% after 30 and up to 5% after the age of 35.

*A maternal history of fraternal twins in your family increases your odds.

*Your chances of having twins increases with each pregnancy, especially if you've already had twins before.

*According to a study in Medical News Today, vegans are less likely to have twins than their dairy and meat-eating counterparts.

*Using In Vitro Fertilization can increase your twin odds up to 25%.

*African Americans have are more likely to have twins than any other ethnicity.

Despite the joy of successfully becoming pregnant with twins, most women don't understand the risks involved with a multiple birth. A twin birth is generally considered high risk, as twins are more likely to be born prematurely. This can result in low birth weights, under development, and other complications.

But the question remains. With the combination of Hollywood's twin baby boom, women waiting until their 30's and even 40's to have children, and the availability of fertility treatments, will twins become as commonplace as singles?