Martin and Emma Wackrow with newborn daughter Olivia, who was born in Britomart Station's women's toilets.

Auckland's busiest train station has been boasting about better arrival times, but no one expected this passenger to arrive early.

Baby Olivia Wackrow was born on November 5 at about 4pm at Britomart Station after her mother, Emma Wackrow, went into early labour inside a cubicle in the transport centre's women's toilets.

The Wackrow family had arrived in the CBD by train from Avondale and were walking up Albert St to meet friends for dinner when Emma started to feel very uncomfortable.

DAVID WHITE/STUFF Emma Wackrow says she went to the toilet not know she was about to give birth.

"The baby was really moving a lot, it was quite painful," Emma said.

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"But I didn't really think anything of it because she had been doing this for a couple of weeks, then over the next 20 minutes it kept happening, and I thought 'this is unusual'."

DAVID WHITE/STUFF AT customer representative and student nurse Ashley Lang helped deliver the baby in the Britomart women's toilet.

The Avondale residents decided to head back to Britomart to take the next train home, but upon arrival Emma had an overwhelming urge to use the toilet.

"The whole thing happened within a space of 10 minutes, from going into that bathroom to holding her in my arms.

"It's funny just how the human body knows what to do, instinct kicked in and everything took care of itself really."

DAVID WHITE/STUFF Baby Olivia Wackrow was born in stall one of the Britomart women's toilet.

While in the toilet there was no time for Emma to panic as she was focused on keeping her 2-year-old son Luke calm, she said.

"I didn't want him to see me in pain. He kept saying 'are you OK mummy?'

"And I was saying 'yeah mummy is fine, mummy's just got a sore tummy'."

Even with all the commotion inside of the bathroom, commuters surprisingly continued to enter it and use the toilets, she said.

"The worse thing was they kept using the hand dryer and Luke is really scared of it, so I screamed 'stop using the hand dryer you're scaring the toddler!'."

Meanwhile, Auckland Transport (AT) customer representative and student nurse Ashley Lang was busy selling HOP cards when her friend and co-worker Vivi Tiavolo rushed to her booth.

"She said someone was screaming and giving birth in the bathroom and could I come and assist," Lang said.

The baby was most of the way out when Lang entered the bathroom stall, she said.

"I let her do her thing for a minute, then I introduced myself and we got busy delivering the placenta."

Lang, who was eight months pregnant herself, had delivered fake babies while studying midwifery, but had never done the real thing before, she said.

"I was really shocked, I think adrenaline kicked in and I was glad she was as easy of a birth as it could be, nothing tragic happened."

This was the fastest birth Lang had ever seen, as labour usually took between five to seven hours for women giving birth for the second time, she said.

Lang said she was worried while delivering the baby hers would get the same idea.

"Maybe Emma will show up to my birth and help me deliver."

Emma's husband Martin Wackrow said the situation was very intense and a lot happened really quickly. ​

AT spokesman Mark Hannan said this was the first baby to be born inside of the station.

The Wackrow family will be receiving a HOP card with $100 on it to thank them for their support for public transport, he said.