A woman who was admitted to hospital to have painful ovaries removed and came home with a baby is due to find out how the advanced pregnancy was missed.
Rebecca Oldham, 25, said she had three scans, two blood tests and six pregnancy tests to try to explain severe abdominal cramping.
She was admitted to Middlemore Hospital in November last year to have her ovaries removed but doctors instead discovered a full-term, 4kg (9lb) baby.
The case has been described as extremely rare by doctors who are investigating how the pregnancy was missed.
Last week Oldham told the Herald on Sunday that she was due to see the findings of the investigation and hoped it would provide closure for herself and partner James Tipene.
The pair were already parents to Hayley, now 20 months, when they welcomed their unexpected son, also named James, into the world.
"I was facing not being able to have any more children because they thought there were problems with my ovaries and all of a sudden we had a son," Oldham said.
Doctors woke her and told her the news before performing an emergency caesarean.
"I am so glad they woke me and told me I was going to have another baby," Oldham said.
"Even though it was short notice it was better than waking up and being handed a baby."
Oldham has since been told the stomach pains she had been experiencing were probably because James had lodged tightly along her back.
Becky Oldham with surprise son James Tipene.
"He was lodged in, even with the caesarean they had to use forceps to get him out," Oldham said. "They think the pain was caused by him trying to move around but he couldn't."
Oldham said she struggled with feeding James, perhaps because she hadn't spent time being aware of the baby coming.
"I had no idea, I couldn't grasp breastfeeding," she said.
"I think it was because my body wasn't emotionally aware I was pregnant.
"When he cried at night I would say, 'ssshhhh Hayley', and then remember it wasn't her and that I had a newborn baby.
"He's a good baby, he's teething and has half a mouth of teeth already. People say 'how could you not know?' But I really didn't.
"I can't explain why but it was scary not knowing."
Middlemore Hospital spokeswoman Lauren Young said staff acted entirely appropriately in the case.
She could not comment further as Oldham had not waived her right to privacy.
Oldham has since moved to Australia because her partner was offered a job there.
Hard to miss foetus of 32 weeks on a scan
Auckland obstetrician Dr Martin Sowter believes a positive pregnancy result should have shown up at some stage of testing.
He said there were often errors with home pregnancy urine tests because they were sometimes misused but a hospital blood test would always show some of the HCG pregnancy hormone from eight to nine weeks' gestation.
"After eight or nine weeks there will always be some pregnancy hormone floating around."
He said the only way a scan could not detect a pregnancy would be if a woman was extremely overweight or obese.
"In that case they might have trouble finding the uterus but if they could find the uterus they should have been able to see something in it. Especially if it was a 32-week-old foetus.
"If an ultrasound is conducted properly you will always see something. The only way you might miss that is if you were looking at the wrong scan or if the person doing the scan didn't know how to use the equipment properly."
When things have been missed in the past it has been because they were looking at another patient's report.
Sowter said about one in 500 women didn't know they were pregnant until late in the pregnancy.