Called the V-steam, the treatment involves perching over an open stool, above a steaming brew of herbs.
Hollywood celebrities such as Tia and Tamera Mowry and Gwyneth Paltrow have jumped on the bandwagon, with Paltrow apparently endorsing it in her blog: "You sit on what is essentially a mini-throne, and a combination of infrared and mugwort steam cleanses your uterus, et al.
"It is an energetic release - not just a steam douche - that balances female hormone levels. If you're in LA, you have to do it."
Others have likened it to a down-under facial, and it costs anywhere from US$20 (S$27) to US$120 in the US.
But the vaginal steam bath has been around for a long time.
In Singapore, it is available as a traditional Javanese treatment in some spas.
Meant for women who have recently given birth, "ganggang" as it is known here, tightens the vaginal area and heals tears after delivery.
In Korea, this treatment is called "chai-yok". Its practitioners believe it can reduce stress and regulate menstrual cycles.
In South America, a similar treatment is called "bajos".
Echoing the trend in California, in the US, local spas say they notice that women who are not new mothers are asking for the treatment too.
"Just over 10 years ago, it was only mothers but we have started getting brides-to-be and other women coming in now," says Madam Ally Vijay, owner of Babies Bellies Javanese Massage & Spa, which has outlets in Golden Landmark and Square2 in Novena.
She claims that the increase in younger clients has to do with the other benefits of the treatment.
"Not only does it tighten, it also cleanses the area," Madam Ally says. "It helps remove odour."
Owner of SpaJelita at Changi Road, Madam Fadilah Majid says: "Our clients are getting younger and younger. A lot of them are starting to do it for its cleansing benefits.
"In most of their feedback, the customers say they see less discharge."
Babies Bellies Javanese Massage & Spa charges $60 for 15 to 20 minutes. At SpaJelita, it is $48 for 30 minutes.
The spas would not reveal their recipe of special herbs used in the process, but The New Paper on Sunday understands that there is ginger and lemongrass in the mix.
Bride-to-be Siti Nurul Ain, 29, who is tying the knot this weekend, told TNPS that she went for a ganggang treament on Wednesday in preparation for her wedding night.
"My fiance is Javanese and when I told him I was going, his reply was, 'That's good, that's good'," she says with a giggle.
Miss Reza Natasha, 26, says she is a fan, especially of its supposed cleansing properties: "I know a lot of people don't believe old wives' tales but I have seen the difference and that's why I will continue going for ganggang."
When TNPS checked with doctors, Dr Christopher Chong, a obstetrician and gynaecologist at Gleneagles Hospital, says that results can't be "based purely on observation".
He says: "For tightening, the minimum you need is laser therapy for the collagen inside the vagina to change.
"There hasn't been one proper medical study on the method. So it is not logical to deem it a successful way of doing any of the things it claims."
This article was first published on April 6, 2015.
Get The New Paper for more stories.