The MTA started handing out bright yellow buttons saying "Baby on Board" for pregnant subway riders to wear so that other passengers know when they should get up and offer their seats, officials said.

Beginning on Sunday, as part of a new awareness campaign to remind passengers to give up their seats for those in need, the MTA is distributing buttons with two messages — “Baby on Board!” and “Please offer me a seat” — that alert straphangers of pregnant, disabled or senior riders.

Those commuters “often need seats more than others but their condition may not always be visible,” said MTA interim executive director Ronnie Hakim in a statement. “We hope this campaign will help their fellow riders to be more willing to offer them a seat without having to ask a personal question first.”

About 14 of every 1,000 people living in New York City gave birth in 2014, according to the most recent data from the city’s Health Department.

Offering your seat for the city’s disabled population is more than a kind gesture; it’s required by federal regulations and MTA rules of conduct for those occupying designated “priority seating” on subway trains and buses.

“A little courtesy goes a long way,” said Veronica Vanterpool, executive director of the Tri-State Transportation Campaign and MTA board member. “Providing a seat to a special needs user, without having an awkward conversation, can make a big difference with a small gesture.”

The button campaign, a pilot program running through Labor Day, was inspired by an effort in London that launched back in 2006. Since, Transport for London distributes more than 100,000 similar badges each year to London Tube riders entitled to priority seating.

At the MTA, the button movement will join a list of “Courtesy Counts” campaigns geared toward making cramped mass transit more tolerable. That includes an offensive against manspreading and more.

Riders can request a free button through the MTA website by filling out a form with no documentation required. Buttons will be shipped in about three weeks, according to the agency.