In the chic offices of Stitch Fix, a newly public company flush with cash, state Sen. Scott Wiener, D-San Francisco, introduced a bill Monday that would ensure most California women have access to lactation facilities at work.

This bill mimics a recently implemented San Francisco ordinance, which as of Jan. 1 required businesses — both public and private — to provide lactation facilities to their workers by 2019, or face fines. Lactation rooms in offices mean mothers won’t have to choose between staying at home to express milk or doing it in an uncomfortable environment, like a restroom stall.

“This ensures that new mothers can make their own decisions on their timetable for returning to work, rather than having that decision made for them,” said Wiener, flanked by Supervisor Katy Tang, who introduced the San Francisco ordinance; Assemblyman David Chiu; and other advocates for the bill.

According to the bill, lactation facilities must be built into new construction larger than 15,000 square feet. For existing buildings, the bar is lower: As long as it is a private room that’s not a restroom, with a couch, table and nearby access to water and a refrigerator, it counts.

“It’s not just the right thing to do, it’s the smart thing to do,” Stitch Fix CEO Katrina Lake said. Lake, who has been applauded for her focus on women’s rights in the workplace, runs a company that is predominantly female. Stitch Fix offers a personal styling service where customers subscribe to periodic deliveries of selected clothing.

Lake said she used Stitch Fix’s lactation rooms herself for several months after giving birth. The company offered a tour of one such room with a gray couch, a medical-grade breast pump, a mirror and a table with a box of tissues.

According to the Eunice Kennedy Shriver National Institute of Child Health and Human Development, breastfeeding has many health benefits for both infants and mothers. Among them are protections against common childhood infections, and a lower risk of sudden infant death syndrome. Store-bought formula can also be very costly.

Stitch Fix, with its multi-floor offices in the heart of San Francisco’s Financial District, has plenty of room for multiple lactation rooms (which it had before the local ordinance was passed). But in a city with an already tight real estate market, creating an extra room — even one that just requires a couch and table — could be seen as a burden for smaller businesses.

Elaine Wherry, co-owner of Dandelion Chocolate in the Mission District, said her company got creative, using a 4-by-4-foot canopy tent, with seating and access to a fridge and water.

“We don’t have the budget or the space of other institutions,” she said.

If a company believes complying with this law will create a burden on its bottom line, the bill allows it to apply for a hardship exemption. The San Francisco ordinance, which drew support from the city’s Chamber of Commerce, has a similar provision.

Chiu admitted he wasn’t aware this was a problem women faced until he and his wife had a child of their own.

“This is a bill about ensuring that breastfeeding continues to be the dominant form in which we are helping to provide nutritional supplements to our children,” he said, after joking that he subscribed to Stitch Fix’s personal styling service as a gift to his wife while she was pregnant. “We also know that the alternative to breastfeeding is expensive — I’ll tell you that I was shocked to discover how expensive formula is.”

Trisha Thadani is a San Francisco Chronicle staff writer. Email: tthadani@sfchronicle.com Twitter: @TrishaThadani