The grateful new parents, Grey Lynn couple Keely O'Shannessy and Nick Dravitzki - whose frozen embryo was unfrozen and implanted in Ms Gracen, making Leo their biological child - never doubted Ms Gracen would follow through.
"She did exactly what she said she would do. It was like she couldn't wait to give him to us and see us all together," Ms O'Shannessy said.
Ms Gracen, now 43, said: "It was the most amazing thing watching their faces. They had had to wait that length of time and trust I would hand him over".
Even when Leo was in her arms, Ms O'Shannessy was still so worried about her surrogate that she could barely focus on the baby.
"It's the hardest thing to witness someone in that much pain because they are doing something for you. It didn't really feel like I could start to be a real mum until I had got him home."
Ms Gracen is one of an increasing number of New Zealand women offering to be a surrogate mother for couples who cannot have children on their own.
In 2010-11, there were 25 applications for clinic-assisted surrogacies, compared with 15 in 2005-06.
Only about one-third of those applications go ahead owing to many factors including a failed implant or an embryo not surviving the thawing process.
Surrogacy applications approved since 2005 have so far resulted in 26 live births. Fifteen surrogacy applications from last year are ongoing.
Assisted reproduction expert, Associate Professor Wayne Gillett, said surrogacy had been occurring in New Zealand as far back as the 1980s. However in 2004, the Human Assisted Reproductive Technology Act became law.
This put controls in place "to the point that no surrogacy can occur in New Zealand without approval by an ethics body ... that looks at all cases on a case-by-case basis", Dr Gillett said.
Counselling is also considered an important of the process.
"Most cases are straightforward I think. But the overall success of (surrogacy) is not great.
"It's a lot of hard work for all people involved for a few positive outcomes."
By law, surrogates cannot be paid in New Zealand, but in some countries women do receive payment.
International A-List celebrity couples who have used surrogates include Nicole Kidman and Keith Urban, Sarah Jessica Parker and Matthew Broderick, Neil Patrick Harris and David Burtka, and Sir Elton John and David Furnish.
In Ms Gracen's case, the former nanny offered to do it for friends. Ms O'Shannessy, having received invasive treatment for cancer, was no longer able to have children.
However the couple had embryos - created from Ms O'Shannessy's ovum (egg) and Mr Dravitzki's sperm - frozen before the cancer treatment began.
Ms Gracen said it felt quite different to having her own daughter Hazel, now 4, whom she shares with partner Jeannie Grant.
She had worked out in advance that with Leo she was going to go to the home of the parents-to-be when she knew the birth was near.
"So they could be part of the story of their son being born. So they can then tell their story to him."
As it started to get "full-on" and Ms Gracen was no longer "making much sense", Ms O'Shannessy took over.
They met their midwife at Auckland Hospital.
The couple left Ms Gracen's hospital room when her waters broke, and then returned, and an hour and a half later baby Leo Vincent Dravitzki was born, weighing 4015g.
"It was exceptionally emotional," Ms Gracen said.
"It's not every day that you have a baby and then just hand it over to someone else."
Leo was legally Ms Gracen's son for the first few months until an adoption could be completed. She still sees him about every two to three weeks.
"We hang like friends. Keely's trying to a find a special name for me, which is very cute. Aunty doesn't really work."
Ms O'Shannessy, 35, said she and her husband always felt having a child would be a long shot after her cancer treatment.
The couple started the process with one potential surrogate, but it did not work out, "which was quite heartbreaking".
When the pair met Ms Gracen "she just seemed so perfect".
"It just felt right, and I think she felt the same way."
"She was just astounding all the way through.
"I can't imagine that many people would be able to do it as well as she did it. I'm not religious but ... she was like an angel sent from Heaven."
Ms Gracen urged other women thinking about being a surrogate to do it.
"Don't be frightened. Because it's an incredibly empowering experience.
"There's so many women who need help."
