London Underground (LU) is to give special badges to pregnant women in a drive to encourage people to give up their seats for mums-to-be.
The new badge will make pregnant women identifiable
The badges bearing the slogan Baby on Board would make pregnant women identifiable to fellow passengers.
A spokeswoman for LU said its research found those who needed to sit down felt they could not ask fellow passengers to give up their seats.
If the trial proves popular, badges will go to all pregnant Tube users.
Research also found most travellers believed mums-to-be should be offered a seat.
LU spokeswoman Elizabeth Norris said: "It is sad but true that passengers who need to sit down feel that they cannot ask fellow passengers for a seat.
"Priority seats on the Tube are clearly marked and anyone who really needs to sit down, including pregnant women, should ask."
Officials said they hoped the idea would give women the confidence to ask for a seat and encourage people to offer without being asked.
Emily O'Regan, who is 37 weeks pregnant, travels on the Tube from Wimbledon in south London to St James' Park, central London, everyday and said the badges were a good idea.
'Sick and faint'
"It is sometimes difficult to tell if a woman is pregnant, especially in winter when everyone is wearing extra layers," she said.
"And on a crowded Tube people don't always see your bump.
"But a lot of people just aren't prepared to give up their seat so at least this way no-one can use the excuse that they didn't realise.
"In the early stages of pregnancy when no-one can tell you're pregnant a lot of women feel sick and faint and it can be dangerous if they have to stand up in a crowded carriage.
"A badge would take the awkwardness out of the situation."