A Tauranga couple were given two surprises today when their baby boy was born earlier than expected on what they didn't realise was Tauranga Hospital's 100th birthday.

Madeline Parker and Manuell Korzelius welcomed their fourth baby boy, who is yet to be named, at 4.50am on Thursday, March 6.

Tauranga couple Madeline Parker and Manuell Korzelius welcomed their baby boy at 4.50am. Video: Ross Brown and Zoe Hunter.

The baby, weighing a little more than 8 pounds, was born exactly 100 years since Tauranga Hospital first opened its doors in 1914.

Madeline and Manuell were told of the hospital centenary minutes after their baby was born, but this was not the only surprise for the couple – their baby came earlier than expected.

Exactly a week after her due date of February 27, Madeline was scheduled to undergo a caesarean this afternoon – but instead had a natural birth early this morning.

One hundred years ago, men were not allowed to be in the room when their partners gave birth and Madeline is pleased she did not have to do it alone.

'It was nice to have Manuell with me and that extra support, as opposed to 100 years ago when I would have had to do it on my own,” says Madeline.

Manuell says he wouldn't have wanted to be 'stuck outside waiting”.

'It was just great to be able to be in there straight after the birth and hold my boy.”

Still reeling from the early birth, Madeline and Manuell have not had time to think about the meaning of having a baby born on the hospital's centenary, but say they will inform him of the meaning when he's older.

Tauranga Hospital has played a big part in Madeline's life as she and her two older sons Riley, 10, and Connor, 8, were born at the old maternity unit.

Her third youngest, six-year-old Oliver, was born in the new maternity unit where his new baby brother was born this morning.

A hospital spokesperson says a second mother gave birth around midday today. She expects maybe another two will be born today.

BOPDHB CEO Phil Cammish says the hospital's historic event is an opportunity to reflect on 100 years of innovation and excellence and look forward to an even brighter future.

When the Inspector-General of Hospitals Dr T.H.A. Valintine officially opened Tauranga Hospital in 1914 it had a live-in staff of four, a cow for milk supply, and a horse for staff transport.

The 250m² E-shaped building included two wards (a four-bed male ward and two-bed female ward) and sat in an acre of grounds.

Today the hospital buildings total 58,000m² of floor space and sit on a 12 hectare campus. There are 349 beds and a 2240-strong staff is employed from the Tauranga site.

Much of the hospital's expansion has occurred since the 1950s, up to which point it was still considered a cottage hospital.

'Today we have a modern hospital that can no longer be considered a cottage hospital,” said Mr Cammish.

'We also have a wonderfully dedicated staff practising innovative and sometimes world-leading medicine for the people of the Bay of Plenty.

'I am often told by people how proud they are of Tauranga Hospital, and especially so when they drive past and compare today's modern buildings to the 1950's cottage hospital.”