Ever since Ms Jaya Iyer's daughter was a toddler, she had been fascinated by Saturn and its icy rings.

When Swaha turned three, she had a space-themed birthday party. But when her mum looked for clothes with space images for Swaha, she could not find any. They were all in the boys' section.

So the 41-year-old mother of two, who has a doctorate in fashion merchandising, started her own business called Svaha - which is how her daughter's name is pronounced - selling clothes that up-end gender stereotypes.

One shirt features a grinning green stegosaurus, the plates on its back adorned with polka dots. A second comes in a blazing pink hue, with an astronaut planting an American flag on the moon. That one should satisfy her daughter.

"She was very upset with me for not ever buying her anything with astronauts on it," Ms Iyer says. "Then she started telling me: 'I want a ninja on my shirt.'"

Svaha is one of several start-ups that have emerged in recent years with the goal of changing the standards that govern what kids wear. These upstarts are not looking to replace current kids' apparel entirely. Instead, their founders say they want to provide children with more options.

Handsome in Pink says it is all right for boys to wear pink and purple. Buddingstem offers science-themed garb for girls. Perhaps the buzziest label is Princess Awesome, which raised more than US$200,000 (S$272,700) in a successful Kickstarter campaign, showing demand for pirate- themed dresses and girls' apparel covered in the symbol for pi.

Most of the ventures remain in early stages as online-only entities using crowd-funded or boot- strapped cash to sell small numbers of shirts or dresses.

Several of the start-ups share a common origin: They were born out of parental frustration with major retailers. Simply shopping in the opposite gender's section is not the answer, these parents say.

Cultural norms mean that as children get older, designating certain items as male or female can confuse and frustrate them. A girl may not want to wear something designated for boys and vice versa.

"Most kids and parents are going to the big retailers and seeing all these messages of what it means to be a boy or a girl," says Ms Sharon Choksi, founder of clothing line Girls Will Be.

Her daughter Mya, 10, never liked sparkles or "feminine" colours, so the Choksis would shop for Mya in the boys' section. As Mya got older, Ms Choksi worried that "boy" and "girl" labels would unnecessarily upset her daughter.

She started selling girls' shirts in 2013 before expanding into hoodies and shorts. In an effort to encourage girls to move around freely, the fit of Girls Will Be tops fall between a traditional, fitted girls' shirt and the boxy, looser fit typically marketed to boys.

One design reads, "bold, daring, fearless, adventurous, so many things", while another features a silhouette of a girl doing a flying sidekick.

Ms Choksi, who is from Austin, wants her clothes to fill a gap left open by big companies. "When are the big retailers going to realise that not all girls are the same and not all boys are the same?"

In Seattle, Ms Martine Zoer had similar experiences with her sons. She grew tired of her boys, four and seven, being pushed merchandise featuring designs of dinosaurs and trucks. In 2014, she founded Quirkie Kids, a label devoted to gender-neutral clothes.

"There's nothing wrong with pink or girls liking pink," Ms Zoer says. "But if we offer them only that choice, there's something wrong with that."

"There's nothing hardwired in our brains that says pink is for girls and blue is for boys," says neuroscientist Lise Eliot at the Chicago Medical School at Rosalind Frank University and author of Pink Brain, Blue Brain: How Small Differences Grow Into Troublesome Gaps - And What We Can Do About It.

It is a cultural phenomenon. By the time children are toddlers, Dr Eliot says, boys start rejecting pink because they realise it may diverge from what is expected.

These apparel choices can have enduring repercussions by affecting kids' interests and long-term goals. For instance, as most female clothes are more fitted, they often double as restraints, she says, pushing girls away from physical activities.

Kids' play habits matter because they affect development and, ultimately, even what career they end up embracing.

If a girl is tugged away from liking outer space by societal pressures, she probably would not veer towards an aerospace profession later in life. If a boy is discouraged from playing with dolls and wearing bold clothes, they may not want to get into fashion design one day.

Big retailers are typically focused on quantity, so until enough shoppers demand clothes that do not fall along traditional lines, not much will change, says Ms Patty Leto, senior vice-president of children's wear at the Doneger Group, a trend intelligence firm. "Pink is always going to sell for girls and blue for boys," she says. In the end, it is up to the parents.

Take, for example, Lands' End, which in 2014 found itself under attack by angry shoppers when New Jersey mum Lisa Ryder wrote a letter decrying stereotypes in its clothing selection. Flipping through a catalogue, her daughter loved shirts with planets and dinosaurs, though they were clearly marked for boys.

When it was suggested to Ms Ryder by a Facebook commenter that she simply buy a boys' shirt, she responded with vigour.

"The problem is that your recent catalogue copy and product offerings strongly promote the gender stereotypes that young boys are smart and mighty and young girls are adorable," she wrote. "Simply buying my daughter one of your 'boy shirts' is not the answer because it perpetuates the idea that science is a boy thing that she happens to be participating in."

Lands' End decided to release new science-themed shirts for girls.

For the giants of the clothing world, it is an exercise in figuring out what will sell. For the budding brands, it is less a race for revenue than a mission to make a difference.

"Everybody's really supportive of one another, rather than being competitive," Ms Zoer says of the community of new brands. "We're sort of in this together."

BLOOMBERG