Betsi Cadwaladr University Health Board is consulting on plans to withdraw consultant-led maternity care at one of three district hospitals.
Earlier plans to downgrade services at Glan Clwyd Hospital in Bodelwyddan, Denbighshire, were sent back to the drawing board after public outcry.
The proposed changes stem from a shortage of doctors.
Health bosses still favour downgrading services at the hospital and earlier this month the board agreed to start a fresh public consultation on those plans and others.
Alternatives include withdrawing doctor-led maternity care at hospitals in Bangor or Wrexham, or they could agree to make no changes meaning consultant-led care would remain at all three hospitals.
Those against the plans say expectant mothers who need care from doctors would be put at greater risk by having to travel further for treatment.
The British Medical Association and politicians have also previously criticised the health board for not seeking the views of staff and the public in drawing up its plans.
A final decision is expected in November.
About 500 people have protested in Rhyl against possible changes to hospital maternity services in north Wales.