Treatment has involved weekly visits to Buller Hospital for intravenous doses of immunoglobulin, which is thought to lessen Mrs McKessar's antiplatelet antibody production, and regular trips from the couple's Westport home to Christchurch.
The hospital treatment, which takes up to 11 hours, can leave her nauseous, tired and headachy. She's had to go twice a week for the past fortnight.
"It's been not too bad," she said this week. "I've managed to increase the rate of infusion ...That's been helpful because it means I'm getting home by 5pm. But from 8.30am to 5pm is still a full day."
Her body's reaction to the treatment had varied.
"It's really bizarre. Sometimes I'm fine, other times I have bad headaches. I had treatment yesterday - I'm fine today. Last week I was quite sick."
Tuesday morning she had gone to the gym for a gentle hour-long gym workout. "It keeps me sane. I feel like if I'm not getting ready for the hospital, I'm in the hospital or recovering from the hospital."
She returned to Christchurch Wednesday for brain and growth scans of her daughter. Similar tests two weeks ago showed everything was fine.
The baby weighed 1160g - 70 per cent above the average for her gestation. Her blood flow was normal and she showed no signs of anaemia.
On March 2, Mrs McKessar begins three days of steroid doses to help the baby's organs mature before her premature arrival.
Steroids can have serious side affects on the mother, including liver and cardiovascular damage.
After her birth, the baby will go into intensive care and receive a blood transfusion to boost her platelets.
A donor is already lined up in Christchurch.
Mrs McKessar could have been the donor herself "but with everything else going on it's an extra complication we don't need".
She had been told her daughter would be in hospital for up to a month. She could stay with her for five days, then would have to relocate to Ronald McDonald House.
Her husband and two sons from a previous marriage, Blake 12 and Fergus 8, would visit every weekend.
Last year, Kirsten and Luke ran the Buller Gorge Marathon to raise over $12,000 for Ronald McDonald House, which had helped them after they lost their son Carter-Luke.
Mrs McKessar said they would be watching the race from the sidelines this weekend, but she had a tentative deal to run it again next year with a Ronald McDonald manager.
