Roughly half of the human population menstruates at some point in their lives. Women know this. Men know this. And yet, few talk about it openly. From an early age, we're taught that periods are disgraceful and dirty, leaving women feeling embarrassed and alone.

That's one reason why Thinx, a menstrual underwear company "committed to breaking the taboo around menstruation," decided to propose a provocative new advertising campaign for the New York City subway, which acknowledges upfront how frequently periods are shrouded in silence and shame.

According to Thinx co-founder and CEO Miki Agrawal, the campaign pushes the envelope with purpose, relying on suggestive imagery as a way to start a conversation about menstruation stigma. One of the ads shows a photo of a cracked egg, an allusion to the unfertilized eggs expelled during menstruation. Another features a woman in a tank top and underwear, next to a picture of a grapefruit.

"If you look, it could potentially be a vagina, but it's clearly a grapefruit," Agrawal told Mic.

That apparently didn't matter, however, to the gatekeepers who reportedly objected to Thinx's proposal — not only because of the innuendo in the ads, but allegedly because they also contained the word "period."

Thinx/Miki Agrawal

Thinx/Miki Agrawal

What's in an ad?: The Thinx campaign set out to adhere to the advertising guidelines of the Metropolitan Transportation Authority, the corporation that oversees the New York City public transit system. According to MTA guidelines, the MTA prohibits ads that depict "sexual or excretory activities" or materials that promote a "sexually oriented business" — which Thinx, as a company that sells alternative menstrual products, is not.

But that didn't stop Outfront Media, the company tasked with managing much of the MTA's advertising, from declining to approve the Thinx proposal anyway, arguing that the ads were considered too risqué.

In an email exchange obtained by Mic, an Outfront representative told Agrawal that in addition to some of their concerns over copyright issues, several of the proposed ads "seem to have a bit too much skin," adding that the egg and grapefruit imagery, "regardless of the context, seems inappropriate."

During initial conversations with the agency, before Thinx submitted its proposal, a representative reportedly expressed concern that the advertisements would not be approved if they contained the tagline "For Women With Periods." According to Veronica del Rosario, Thinx's director of marketing, the representative was concerned that children would see the word "period" in the ad and ask their parents what it meant. When Thinx later submitted the ad with the word "period" in the copy, the agency told them they could not run the copy "as is."

"I stated [to an Outfront rep] that it was extremely disheartening that [certain other ads] could fly, but something for women that speaks directly to women isn't OK by them," del Rosario told Mic. "He replied, 'This is not a women's issue. Don't try to make it a women's rights thing.'"

A spokesperson for the MTA contacted Mic to confirm that the transit authority did not reject the proposed ads, and had no part in the conversations between Outfront and Thinx. Mic also reached out to Outfront for comment, and received a statement that Thinx's proposed ads had not been officially declined:

Together with our transit partners, OUTFRONT Media makes every effort to assist advertisers in creating campaigns that are both effective and appropriate to the transit environment. This is the approach that was followed with respect to the advertisements proposed by Thinx. No copy was ever rejected and the current copy is still in the MTA review process. We suggested changes that we felt were appropriate for the riding public and were hoping to work with the advertiser to refine the copy.

Thinx

An apparent double standard: But this isn't the first time Outfront has been accused of inconsistently enforcing its standards for what does and does not violate the MTA's guidelines. Earlier this year, the New York Times highlighted several inconsistencies in the company's approval process, centering on the rejection of an ad that featured a pants-less woman with her legs wrapped around a male partner.

The ad in question was declined because it was "too suggestive." Yet similarly racy images — such as those in ads for the film 50 Shades of Grey, for example, or for exhibits at New York's Museum of Sex — have appeared on the subway.

While Agrawal and del Rosario said they have never seen an ad for menstrual products on the New York City subway, the MTA does have a history of approving ads that feature sexual imagery and photos of scantily clad women.

Outfront declined Thinx's ads in their current form because the models showed "too much skin," according to the email exchange between Agrawal and an Outfront rep. Yet a series of controversial breast augmentation ads, which feature close-up images of women's cleavage, began appearing on the subway in 2014.

In 2014, the MTA also approved another ad for the same plastic surgery firm that depicts a woman holding a pair of grapefruits in front of her chest. Del Rosario told Mic that when she asked the Outfront representative to explain why one grapefruit innuendo was considered acceptable when Thinx's use of the fruit was rejected, "he said that the grapefruit breasts don't represent female anatomy."

In a phone conversation with Mic, del Rosario recounted her version of events. "I said they represent breasts, obviously. [The rep] told me representing something is different than 'looking like' something, and that he misspoke," she said. "I [also] asked what, specifically, the egg 'looked like,' and he said it looked like male ejaculation or female fluids."

An ad for breast augmentation that appears on the New York City subway Adrants

The MTA has also hosted lingerie ads featuring scantily clad models. Earlier this year, for instance, the MTA stood by a campaign for the plus-size brand Lane Bryant's lingerie line following protests from ultra-Orthodox Jewish groups. The fitness supplement company Protein World also came under fire for subway ads for its weight loss collection, which featured an image of a young woman in a bikini next to the words "Are you beach body ready?"

Protein World

The future of the Thinx campaign remains unclear.

Agrawal agreed to change what she believed to be Outfront's reasonable concerns about the proposal, such as the potential copyright issues. (An original version of the ad, for example, made a reference to Mary Poppins, which Outfront said likely wouldn't fly.) But she pushed back on the suggestion that her advertisements are too suggestive or inappropriate.

In a follow-up email to Outfront also obtained by Mic, Agrawal pressed the company for an explanation as to why ads that could be interpreted as overtly sexual or objectifying of women are OK, while those intended to empower women are not.

"Just as New York City is potentially about to pass legislation to scrap the tax on feminine hygiene products, the MTA is not letting the word 'period' appear in the subway," Agrawal said. "We can objectify women in their lingerie, but the minute we acknowledge that they might be bleeding in their underwear, it's no longer acceptable.

"This is 2015. This is happening today," she added. "It's crazy."

Update: Oct. 23, 2015

In a statement to the New York Times, an anonymous MTA spokesperson said the Thinx ads will "of course" be approved, but officially remain under review by the agency.

Correction: Oct. 20, 2015