Midwives are being urged to vote in favour of strike action over pay in a ballot that will be held next month.
The Royal College of Midwives (RCM) announced it would ballot its members from November 11 for a period of four weeks on whether to take industrial action.
The union is urging its members in England and Wales to vote in favour of action. A ballot is already under way in Scotland.
Two-thirds of eligible members in England and more than eight out of 10 in Wales have taken part in a consultation on the move, with three-quarters (75%) saying they wanted to be balloted on possible strikes.
All midwives and maternity support workers employed in the NHS who are members of the RCM are eligible to vote.
The RCM has said no action would be taken that puts mothers and babies at risk, with safe services being maintained.
It comes after the Royal College of Nursing (RCN) ballot on strike action got under way on Thursday, with all UK members being asked if they are prepared to walk out over pay.
That ballot closes on November 2.
RCM’s executive director trade union, Dr Suzanne Tyler, said: “Midwives have only taken strike action once in 140 years. This is not something they take lightly.
“The RCM has already called on the new Prime Minster to keep her promises and ‘deliver on the National Health Service’.
“One way to do that is to ensure staff are valued and paid fairly for what they do. It unfortunately appears they aren’t willing to listen or even acknowledge the workforce crisis engulfing our NHS.
“Our members are sending a very clear message to the governments in England and Wales and one that must not be ignored any longer.
“We have previously warned NHS leaders and Governments in England and Wales that staff were at breaking point and a below inflation pay award would see midwives heading for the door. Our members feel undervalued, underpaid, and are now angry that the Government has not listened to them.
“Many are struggling with the rising cost of living and deeply worried about the future. For midwives to consider taking industrial action it is really the last straw, but they feel they have no other option.”
Health workers in other trade unions are also being balloted for industrial action over pay.
Earlier this year, the Government gave most NHS workers a £1,400 pay rise, well below what unions were calling for.