Alicia Anderson said while she received many presents upon the arrival of her daughter Lacey last year, it was the "gift" from strangers which she would always remember.

"After Lacey was born the placenta was stuck and I lost a lot of blood," Mrs Anderson said.

"I had to go to theatre to have the placenta removed and I received four units of blood in a number of transfusions.

"Without that I would have died."

Mrs Anderson wrote the letter - which will now be shared with donors across the state - to let donors know how much their efforts mattered.

"I wanted to give back in some way, to say thank you to all donors and show them a real-life story where their donations have made a real difference," she said. "They gave me a second chance at life."

In her letter she told donors: "Thanks to you I got to hold my baby girl. Thanks to you I got to see her first smile and hear her giggle. Thanks to you I got to see my son Kade beam with pride when he held his little sister for the first time."

Mrs Anderson also attached a drawing by four-year-old Kade which depicted the whole family. She wrote: "Thanks to you when he draws his family I will always be in the picture".

In the past decade, the rate of blood transfusions for Australian women following childbirth has risen 33 per cent. Now, each year around 4800 new Australian mothers will need a transfusion at birth.

More than 17 per cent of expectant mothers also rely on donated blood to help with complications during pregnancy.

Mrs Anderson hoped her letter would also encourage others to donate.

Australian Red Cross Blood Service spokeswoman Jemma Falkenmire said the letter reinforced the fact that while every donation saved three lives, the impact of the donation went far further.

"A donation of blood has a ripple effect from the person receiving the blood right through to their family and friends ... who are saved from the inconceivable prospect of losing a loved one," she said.

Ms Falkenmire said more Australians were being urged to get involved during National Blood Donor Week, which runs until August 3.

"Surgical patients, new mothers and people with cancer all rely on blood donations."

To become a blood donor call 131495 or visit donateblood.com.au