Anthony Maslin and Marite Norris lost their children Mo, Evie and Otis, along with Ms Norris's father Nick Morris, when the flight came down in eastern Ukraine in July 2014.
The Perth couple described the birth of Violet May Maslin as an "amazing gift".
"Violet's birth is a testament to our belief that love is stronger than hate," they said in a statement.
"We still live with pain, but Violet, and the knowledge that all four kids are with us always, brings light to our darkness.
"As Martin Luther King said, 'Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that'."
Malaysia Airlines Flight MH17 was shot down as it flew over conflict-hit Ukraine from Amsterdam to Kuala Lumpur.
Mr Maslin and Ms Norris had stayed in Amsterdam while their children, aged eight, 10 and 12, flew back to Australia with their grandfather.
A total of 298 passengers and crew were killed, including 80 children in total.
The flight was hit by a Russian-made Buk surface-to-air missile.
Western officials and Ukraine's government blame Russian-backed rebels for shooting down the plane.
But Russian authorities have consistently denied responsibility, instead blaming Ukrainian government forces.

She was making dinner in her flat in the Leith area of Edinburgh when she made the discovery.
The woman called for a friend to help contain the animal, only to find it had disappeared.
It was later found in a cupboard and is now being cared for by the Scottish SPCA, which has named him Zak while it tries to trace his owner.
The California Kingsnake is non-venomous but can bite and rattle its tail.
It is thought he may have squeezed through the pipework in the block of flats.
Fiona Thorburn, of the Scottish SPCA, said: "The lady was just about to have her dinner and got a real fright when she reached into the drawer to grab cutlery and found Zak curled up on the knives and forks.
"As she has a phobia of snakes, she called her friend for help to contain him only to discover that he had disappeared from the drawer.
"Thankfully they managed to locate him in a cupboard elsewhere in the kitchen before he sneaked away.
"Zak is quite large for an escapee and it's usually smaller snakes that can squeeze through pipework in flats.
"However, all snakes can be really good escape artists, so there's every chance Zak has an owner nearby who is looking for him."
An Australian couple whose three children died when Flight MH17 was shot down have a new daughter.
[NEXT_CONCEPT]
A woman with a fear of snakes discovered a 2ft-long kingsnake curled up in her kitchen drawer.