The common medical procedure that is booming in the US, but considered controversial in almost every other country has clinics raking in $500 million a year

Americans are spending $500,000 a year to select the sexes of their kids with in vitro fertilization (IVF).

The practice allows parents to choose a particular sex is illegal everywhere aside the US and Mexico, and is thus one of the more controversial across the globe.

Aside from its invasive nature and enormous price tag, one round will run patients at least $20,000, a small price to pay for some struggling with fertility issues.    

However, one doctor at a clinic offering such services has claimed the sex-picking perk draws in 85 percent of his IVF patients alone - a startling statistic given that accounts for five percent of the total $8 billion the practices rake in each year.

The California physician also pointed out a seemingly unlimited ceiling for growth, for a practice meant to a last resort for those who are eager to be parents but who face obstacles when it comes to conceiving.

The treatment, as of writing, is on the rise, he and other doctors said - especially when sex selection is an option.

Pictured, Fertility Institutes in Los Angeles, one of countless clinics across the country that offer IVF with sec sex selection. The practice - illegal in most countries - is now immensely popular in the US

The practice sees patients select other characteristics such as their baby's eye color, before a doctor collects eggs from ovaries to be fertilized by sperm in a lab (seen here). Sex selection IVF rakes in at least $500million a year - five percent of the money brought in by IVF overall

'The market is the size of the human race,' said Jeffrey Steinberg, founder of the Fertility Institutes in Los Angeles, of the assisted pregnancy practice's popularity.

At his clinic, patients can also select other characteristics such as their baby's eye color, as he collects eggs from their ovaries to be fertilized by sperm in a lab.

Participants can also choose their baby's sex - a perk he estimates draws 85 percent of patients alone.

 As for patients, some are same sex couples, while some are just single and attempting parenthood on their own. 

As of writing, 15 states - including California - require insurance plans cover it, though more often than not, the coverage is minimal. 

He told Slate Tuesday how he markets sex-selection aggressively, as figures surrounding selective IVF for sex selection show that it rakes in an impressive amount of cash.

Sharon Moayeri, the founder of OC Fertility in Newport Beach, said more of the same, revealing that for many Americans, the ability to pick sexes is sort of a silver lining - in a sea of doubt created by difficulty conceiving.

However, unlike Steinberg's, her clinic does not heavily advertise sex selection, she said - though she estimates that still some 15 percent of patients arrive solely because of the perk, without any fertility issues.

Sharon Moayeri said that for many Americans, the ability to pick sexes is sort of a silver lining - in a sea of doubt created by difficulty conceiving

A doctor at the medical center at the University of California San Francisco, meanwhile, said that only some patients come in solely for sex selection, but did point out several instances of parents who, once in the building, are more likely to request girls

'The market is the size of the human race,' said Jeffrey Steinberg, founder of the Fertility Institutes, of the assisted pregnancy practice's popularity

The founder of OC Fertility in Newport Beach (pictured), she her clinic does not heavily advertise sex selection, she said - though she estimates that still some 15 percent of patients arrive solely because of the perk, without any fertility issues

A doctor at the medical center at the University of California San Francisco, meanwhile, said that a low number of patients come in solely for sex selection, but did point out several instances of parents who, once in the building, are more likely to request girls - a phenomenon not unique among Americans, Slate found.

The publication spoke to 15 women and a few men who plan on doing IVF solely for the assurance they will conceive a daughter, fueling debate over the degree of control some parents are attempting amid the controversial practice.

Meanwhile, IVF with sex selection is almost unheard unheard of in countries across the rest of the world, 

It is currently allowed for everyone only in Spain, Belgium, Czech Republic, India, Israel, Russia, Ukraine, Mexico and the US, and to only heterosexual couples in Germany, Austria, Italy, UK, Egypt, Saudi Arabia.

The UK is only one among the second sampleset to allow it for single women, while Egypt and Saudi Arabia only administer the practice on married couples, forcing unwed aspiring parents to look elsewhere. 

Costa Rica is the only country to bar the practice fully, with it legal everywhere else with some restrictions. 

However, the ability to completely control the baby’s destiny - from sex to eye color - is offered only in the two North American countries, marketed chiefly to single mothers, same-sex couples, and families with a history of autism.

It is still divisive, an exclusive poll administered by DailyMail.com in March showed, with 60 percent of Americans said the treatment should remain legal, while just 12 percent said it should be illegal, according to 1,000 voters. 

In the US, the ability to control a baby’s destiny - offered chiefly to single mothers, same-sex couples, and families with a history of autism - is still a bit divisive.

In an exclusive poll administered by DailyMail.com in March, 60 percent of Americans of all ages said the treatment should remain legal, while just 12 percent said it should be illegal, according to the survey of 1,000 voters

The highlighted states have laws on the books stipulating that life begins at the moment of fertilization. In Louisiana, the intentional disposal or destruction of a human embryo is illegal

In contrast, 27 percent said they did not know either way. 

The groups with the slimmest majorities in favor of in vitro fertilization (IVF) were Blacks and Latinos, people aged 18 to 29 and Republicans.

By contrast, the largest support was among people over 65, whites, college graduates and Democratic voters.

The results come after the fertility treatment was thrust into the spotlight last month when a court in Alabama ruled frozen embryos have the same rights as children.

 While the Alabama ruling did not directly restrict IVF, it could open the door to wrongful death lawsuits for embryos that are discarded. 

With the threat of prosecution looming, there are fears that doctors will stop performing IVF, limiting access to an already tough to get treatment.

Laura Kerwin, a Harvard-trained psychologist in California, told Slate that while geared toward helping parents, IVF is still 'a moneymaking industry.'

'People need to realize that [clinics] have a fiduciary duty to their shareholders to make money,' she said, citing draws like selecting kids' sex from birt.

'They’re trying to sell you on an option.'