"Motherhood is wonderful, but a lot of women grieve those old parts of their lives," she said.
"Our society is supportive of women becoming mothers, and gives them this perfect ideal of what motherhood should be like -- with the spotless house and well-behaved kids.
"But it doesn't support mums in retaining their passions and the creative part of themselves."
At the centre of Wairama's story is a mother who feels "sad" for reasons she cannot pinpoint.
In a dream, the mother meets a lost child, representing the childlike creative spirit she had buried.
The child tells the mother to "make beautiful pictures", and, using her children's art supplies, she starts painting, and her depression begins to ease.
Tilyard, herself a mother of five, strongly related to Wairama's tale.
"I found I had to hold on to my creativity -- even sketching for about 10 minutes a day helped.
"I showed my older kids the bit where she goes into the children's room and takes the paints, and they said, 'oh Mum, that's something you'd do'."
Tilyard said Wairama first approached her with the concept for The Mother's Child 10 years ago, and the women consulted a publisher.
The idea was turned down and, due to family commitments, put on the backburner until recently, with Tilyard spending much of 2014 and 2015 on the illustrations.
She relied on colour symbolism to tell the story, using monochromatic grey representing the mother's depressive state of mind, breaking it up with streaks of colour as her creative journey unfolds, and then using bright shades of yellow, teal, magenta and mandarin as her mood lifts.
"When illustrating, you add something to the story rather than just painting exactly what the words say."
She said working on the book took a lot of discipline.
"At one point, I had about 30 illustrations to do, so I made myself do one every day for a month."
The Mother's Child will be available at Aratoi, King Street Gallery and Greytown Art Shop.
