A private hospital in Christchurch has turned away labouring women and sent home some mothers with newborns early due to staffing shortages.

St George's Hospital has confirmed several mothers and babies were impacted by closures at the hospital on Tuesday night.

St George's Hospital chief executive Blair Roxborough said "due to an inability to adequately staff our Maternity Centre overnight on Tuesday, St George's Hospital paused referrals of mothers and babies from Christchurch Women's Hospital."

Following a review earlier this year, the hospital was set to shut down its primary birthing services and post-natal care.

However, Roxborough later confirmed the birthing unit would stay open until at least June 2023.

Te Whatu Ora Waitaha Canterbury (formerly known as Canterbury DHB) also announced a new central city primary birthing unit would open in early 2023.

The Herald understands a labouring woman had to be redirected 30 minutes from St George's to Rangiora Hospital, with her midwife missing the birth and her birth plan being changed at the last minute.

"It's saddening," said the incoming Chair of the College of Midwives Sheena Ross.

"We build our relationships with our women for nine months - for them to not have us present at the birth is upsetting," she said.

"It wasn't the birth she wanted and that was taken away from her which is stressful," she said.

St George's Hospital confirmed three mothers and babies already at St George's were discharged home earlier that day.

One of those women was sent home at about 7pm on her second night in the hospital.

National's Health Spokesperson Dr Shane Reti said it was both "unacceptable" and 'potentially dangerous.'

"In my career, I have been privileged to deliver dozens and babies and that period pre-delivery, the delivery time and immediately post-delivery are really important for a healthy mum and a healthy baby," he said on Newstalk ZB's Canterbury Mornings.

"It's very disappointing to imagine that people can't deliver their babies in the place they planned and prepared for," he said.

It comes as healthcare institutions across the country are under pressure due to staffing insufficiencies.

"The challenge of the staffing shortage experienced by St George's Hospital this week is indicative of the national shortage of midwives being experienced by hospitals and primary birthing units around the country," Roxborough said.

He said, "St George's Hospital continues to actively seek additional midwives to support our maternity services."