Call to keep 'local' maternity services in Pembrokeshire
About 600 protesters gathered at Withybush Hospital in Pembrokeshire to protest against plans to transfer neonatal services to Glangwili in Carmarthen.
Campaigners, carrying banners and placards, fear the proposals could lead to the further downgrading of services.
Hywel Dda Health Board says the plans are part of a wider reorganisation.
It said there was a need for trainee paediatric doctors working nights on call to be based at one hospital.
The board said if it felt unable to maintain full paediatric rotas across the three current sites - Bronglais, Withybush and Glangwili - then the service in the south of the region would be provided from Glangwili Hospital.
"Our intention remains to retain a paediatric, gynaecology and obstetric presence at Withybush Hospital, however this remains subject to further discussion with the scrutiny panel and clinicians," added the spokesman.
One of the protesters Angela Mathias, from Neyland, told BBC Wales reporter Aled Scourfield she had joined the demonstration because her baby granddaughter had been treated at Withybush and she wants local facilities.