She had suffered similar symptoms two weeks earlier and went for tests at the hospital to find out her baby was fine. The second time it happened, the doctor gave them the diagnosis after only looking at her blood test results.
Mr Muir asked for an ultrasound to double check, but was told there was no point, Miss Waitokia said.
They went for a specialist follow-up appointment to determine what had caused the miscarriage, but as soon as the scan came up on the screen, the baby was "jumping around ... and you could see the heartbeat," Ms Waitokia said.
"We just started crying, we were just super happy, we were jumping up and down ... it was a happy moment but we weren't too happy with the doctor that diagnosed it."
Whanganui District Health Board surgical services clinical director Mark Stegmann said the doctor's miscarriage diagnosis was understandable given Miss Waitokia's clinical presentation.
But a definitive diagnosis of miscarriage should not usually be made without confirmation, either by a repeat blood test some days later or by an ultrasound scan, Dr Stegmann said.
The doctor "regrettably" told the patient she had miscarried before they had this confirmation.
The doctor in question discussed the blood test result with a senior doctor and referred her to the early pregnancy clinic for confirmation the following day.
It was not a case of one doctor making a judgment call on their own and there was no indication that an urgent ultrasound scan was needed, Dr Stegmann said.
"The health board regrets that this happened and we acknowledge how upsetting it would have been for the patient and her partner."
Miss Waitokia, who quit smoking when she found out she was pregnant, immediately went home after the diagnosis and had a cigarette.
"If it wasn't so late we would have stopped at the bottle store and drowned our sorrows as well," she said.
The couple, who have two other children - a 2-year-old girl and a 10-year-old boy - have laid a complaint with the hospital over the incident.
"I don't think it was the hospital's fault," she said. "We just want the doctor to learn a bit more about pregnancy."