Mothers relax on the grass with their babies at Central Park during a warm day in New York, March 22, 2012. REUTERS/Lucas Jackson A ski home in Aspen? A private jet? A closet full of Birkin bags?

If you thought any of these were the ultimate status symbol among the millionaires and billionaires of New York City's Upper East Side — one of the biggest enclaves of wealth on the planet — you'd be wrong.

The ultimate status symbol, according to Wednesday Martin, Ph.D., author of the newly released memoir "Primates of Park Avenue," is a whole mess of kids.

"I quickly became desensitized to massive families — they were everywhere," writes Martin, who moved from the West Village to the Upper East Side to raise her family.

"Three was the new two, something you just did in this habitat. Four was the new three — previously conversation stopping, but now nothing unusual. Five was no longer crazy or religious — it just meant you were rich. And six was apparently the new town house — or Gulfstream."

When you think about it, it's logical that a big family equals a big status symbol: It's expensive to raise kids anywhere, and especially in New York City, where full-time nannies, private school, and summer camp are standard expenses. In the US, the average cost of raising a child is $245,340, according to a recent government report. But that figure more than doubles — to $540,514 — when that child is being raised in Manhattan.

Some of the city's top preschools charge as much as $40,000 a year in tuition, and tuition for private grade school can be even higher. Think of a family with six kids, each attending two years of preschool and 13 years of grade school, and that's millions of dollars for education alone, inflation aside.

Children slide down Cedar Hill on a toboggan in Central Park in New York December 17, 2013. Several inches of snow was forecasted to fall across the northeast U.S. on Tuesday as winter storm warnings were put in place, said the National Weather Service, according to local reports. REUTERS/Carlo Allegri Martin is not the first person to see supersized families as a status symbol for rich urbanites. Back in 2011, The New York Post wrote about the trend of large families in Manhattan, citing a study by the Council on Contemporary Families that had noted a "significant" uptick in families with three or four children among the top 2% of US households.

And Tina Fey even addressed it in a 2011 essay she wrote for The New Yorker about working moms, and how rude it is to ask a woman "Are you going to have more kids?"

She wrote:

I thought that raising an only child would be the norm in New York, but I’m pretty sure my daughter is the only child in her class without a sibling. All over Manhattan, large families have become a status symbol. Four beautiful children named after kings and pieces of fruit are a way of saying, “I can afford a four-bedroom apartment and a hundred and fifty thousand dollars in elementary-school tuition fees each year. How you livin’?”



On the Upper East Side, not only are the kids themselves status symbols, they also give mothers the opportunity to preen in front of one another and to forge their own identities, Martin writes in "Primates."

... in a highly competitive culture, 'successful' offspring are status objects — and mirrors," she writes. "Promoting them, working assiduously on their behalf, is a vocation. Being a mommy here is a cutthroat, high-stakes career, stressful and anxiety-producing precisely because it is ours alone to fail at, leading to the success of failure of our offspring. And ourselves.

...

This explained why Upper East Side mothers all wore tiny medallions engraved with their children's initials around their necks. And stacking rings, one for each child, on their fingers.

So if you really want to flaunt your wealth on the Upper East Side, scrap your plans to buy a waterfront home in the Hamptons and have another child instead.