“Obviously we care about our marketing, but we have to have a qualified team,” Klein said, pointing to his years of experience working at a traditional fertility clinic where he oversaw a multitude of egg retrievals, and to Extend’s state-of-the-art lab, overseen by embryology expert Dr. Leslie Ramirez.

“We started with doctors and an embryologist, and only from there did we go out to the world and not the other way around.”

Klein’s team also eliminated a formal waiting room and hired fertility coaches who remain consistent points of contact for patients, in a sort of concierge capacity.

Extend has also agreed to freeze the eggs of Instagram influencers for reduced rates in exchange for posts promoting their experiences at Extend to their thousands of followers. Trellis Fertility Studio will also pay social media influencers to help spread the word about its egg freezing services.

Trellis courts its patients with spa-like amenities, including Turkish-cotton bathrobes for patients to wear during exams and procedures. Mary Pflum

Trellis courts its patients with spa-like amenities, including Turkish-cotton bathrobes for patients to wear during exams and procedures, fresh flowers placed throughout the studio and a juice bar. It’s additionally named its examination rooms after powerful women like Malala Yousafzai and Oprah Winfrey in keeping with the empowerment-themed setting Trellis leaders say they want to establish for their patients.

As part of Kindbody’s “pop-up events” strategy, the company slapped its logo on a bright yellow van similar to a food truck — what it calls the first mobile fertility lab — to court potential patients. Ads announcing where the van will be parked next have attracted crowds of hundreds of women, Silver said.

Silver says women have lined up around the block to get fertility assessments from the van, including a blood test that measures a woman’s AMH level, a hormone used as an indicator in determining her ovarian reserve. Coming soon, Silver says, will be Kindbody’s first fertility bus, which will include ultrasound equipment and operate as a mobile clinic.

Kindbody's bright yellow van, which the company calls the first mobile fertility lab, is used to court potential patients. Kindbody

Patrizio is worried the bells and whistles are there to intentionally distract patients from asking important questions.

“They are trying to convince you to do something that seems to be extremely easy, when it’s not,” Patrizio said, pointing to the medical complications that can arise from egg retrievals and the difficulties associated with thawing and successfully fertilizing previously frozen eggs.

“At the end, you’re not freezing success,” Patrizio said. “You’re freezing a chance. It’s not the same as when you buy insurance for your house or a car. There’s no guarantee that you’ll be able to use the eggs — there’s no guarantee there’s a baby at the end, and you need to know that.”

The ultimate test for the new crop of egg-freezing establishments, though, will come when clients decide they want to have children — and the boutiques can say the eggs they’ve retrieved have finally resulted in actual babies.

Extend Fertility has been around for nearly three years — and, so far, has no baby to show for the thousands of eggs that it has frozen.

“It’s a lag-time issue,” Klein said, noting that no babies have been born yet because most of Extend’s clients are intentionally putting off parenthood. Klein predicts Extend will be able to share news of its first baby “in the next few months.”

How many babies will ultimately be born from all of the eggs the studios freeze remains the big question.

Silber points to a 2014 report by Dr. Ana Cobo of the Valencia Infertility Institute in Spain, one of the few clinics worldwide to have introduced an egg-banking program for its egg donation and fertility preservation patients. The study found that it takes 40 eggs, properly frozen, to provide one woman with a 97 percent chance of having a baby.

The number of eggs retrieved per egg-freezing cycle varies from woman to woman, but often does not exceed 10 to 15 eggs, according to Silber, meaning a woman ideally needs to undergo multiple egg retrievals to increase her chances of getting pregnant — something many women may not be aware of.

“I think there’s going to be a lot of lawsuits,” Silber said. “When they thaw those eggs, there are going to be a lot of nonpregnancies and then women are going to be told there should have been 40 eggs frozen, not 10.”

The leaders of the egg-freezing boutiques NBC News spoke with insist they’re giving women all of the information they need and they are upfront about the risks.

“I would never say it is an insurance policy,” Extend’s Hogarty said of egg freezing. “I say we’re giving you a boost.”

Lisa Wright, 37, said that after undergoing her egg retrieval at Extend Fertility two years ago, she felt “empowered, because I had control.”

Wright, a Delta Airlines pilot, had gone through what she calls a “gut-wrenching” break-up prior to her retrieval, and wanted to enhance her chances of eventually becoming a mother.

She went through one cycle at Extend and froze 13 eggs.

“I treated it like an insurance plan,” she said. “It maximized my chances. I feel like I did everything I could except for starting a family prematurely.”

Lisa Wright, a Delta Airlines pilot who went through the egg retrieval process. Courtesy Lisa Wright

Asked how she’ll feel if none of her frozen eggs eventually result in her having a baby, Wright paused.

“With insurance, you have to hope for the best,” she said, sighing. “But if it doesn’t, it probably wasn’t part of the grand plan.”

Silber predicted that many of the current crop of egg boutique investors will get out of the industry after turning a profit, and before most of the eggs have been thawed. He wondered what will happen to the eggs frozen at stand-alone studios and boutiques if some of them fold or merge before one-time patients come back to use their eggs.

Silver says she believes the egg freezing boutique business model is here to stay.

“We are trying as fast as we can to set up new clinics. The demand has been overwhelming,” she said. “As women keep having children later and keep wanting to keep all their options available, I see it only increasing.”

Silber’s advice to women: ask questions, lots of them, of anyone seeking to freeze their eggs.

“Women should be asking a whole range of questions of these establishments,” Silber said. “Questions like: ‘What is your profit margin? How do you know the eggs will be good when you thaw them? All of your studies have been done on 22-year-olds and I’m 35 — what are statistics for 35-year-olds? Do you guys do the thawing?’"

“I think many women are intimidated to be asking these questions. But they need to ask them.”