Thursday's industrial action comes more than a month after the NSW Nurses and Midwives' Association first voted in favour of statewide action that subsequently saw demonstrations at 150 public hospitals.

Nurses are demanding a nurse-to-patient ratio of one-to-four on hospital wards and a midwife-to-patient ratio of one-to-three, as well as a 4.75 per cent pay rise versus the 2.5 per cent a year allowed by the state government.

"Patients play Lotto depending which day they go to hospital," union General Secretary Brett Holmes told AAP.

"They (patients) could get lucky and get a properly staffed shift or they could get unlucky.

"So our members ... want to see a better health system that will guarantee that there are enough nurses ... to look after patients."

Mr Holmes said the government had not extended an offer to the union since its last meeting with Premier Dominic Perrottet, who has been on two and a half weeks' paternity leave since March 17.

Nurses from up to 170 hospitals took part in a series of rallies on Thursday in Sydney, Albury, Bathurst, Broken Hill, Dubbo, Goulburn, Newcastle, Orange, Port Macquarie, Wagga Wagga, Wollongong and other areas.

They will also protest outside Parliament House, where the NSW Greens will on Thursday introduce a bill to the upper house to legislate the union's preferred nurse-to-patient ratios.

IN OTHER NEWS:

Ms Faehrmann noted Queensland and Victoria had already legislated nurse-to-patient ratios and South Australia was considering the issue.

The union said life-preserving services will be maintained at all public hospitals throughout the day.

The NSW government had successfully argued to the industrial relations umpire the strike should not go ahead, but the union has defied the decision.

The latest strike comes after some NSW paramedics took industrial action on Tuesday with similar demands for improved resources and staffing.

On Monday, the paramedics union shared photos of ambulances queuing outside hospitals including Royal Prince Alfred, Wollongong, Wyong, John Hunter, Concord and others, waiting to offload patients at emergency departments.

When Melissa* signed up to become a midwife, she imagined a rewarding career where she would be able to make a difference in the lives of women and newborn babies at one of the most vulnerable times in their life.

Instead, just weeks into her first year, she wants to quit.

"Basically we're waiting up to four or five hours to have our first toilet break, we're not getting lunch breaks, we're dehydrated, we're caring for new mothers and we don't have time to give them any assistance or help because we're having up to 12 women to care for per midwife," she said.

"I'm five weeks into my career as a midwife and I already want to quit. I think in the past five weeks of work, I've gone to the toilet twice at work because we don't have time for that.

"It's so different from what I imagined. You're responsible for all these women and babies who come to you in a vulnerable state, and we can't give them the care they deserve. It's so disappointing."

The young nurse, who spoke on condition of anonymity, was among hundreds who attended the Wollongong march and rally.

Wollongong midwife Emma Gedge spoke to the crowd at the Wollongong rally in MacCabe Park, reading out a statement from one of her colleagues who was sleeping after night shift.

"She was looking after 10 mums and 10 babies on her own in the postnatal ward - and this is a normal shift," Ms Gedge said.

"She says 'Most days we can't even give the bare minimum support and there are too many days when I leave work feeling defeated because I couldn't give some of the women in my care more than 15 minutes of my time during an eight hour shift."

"Ratios would ensure we never have another shift where I'm asked to care for up to 14 mothers, plus their babies who under this current system aren't even counted as patients. This means that on some days I am asked to care for up to 28 people - mothers and babies - and this is beyond intense, it is not safe."

-with Australian Associated Press