Everly Rose Mostert was born on Tuesday, as announced by Marwood via her Instagram page.
“Everly Rose Mostert 26.03.24,” she wrote.
“We are so in love with our precious little girl.
“She is a dream come true.”
Mostert replied to the post simply with three heart emoticons, while a number of other Supercars drivers offered messages of congratulations to the family.
The addition to the household continues a whirlwind 12 months for the pair, who have been a couple since 2019.
View this post on Instagram
They became engaged when the Walkinshaw Andretti United driver proposed to Marwood last May, just days after the tragic stillbirth of Hazel.
Marwood wrote on social media in November, when announcing her latest pregnancy, “This year has taught us that nothing in life is guaranteed but also that anything is possible.
“7 months ago our hearts endured a loss but also a love like no other, a love that never dies, but can continue to grow.
“I am so grateful to be able to share that we are expecting a little miracle sent from our angel in the stars, Hazel’s little sister.”
Mostert will presumably be kept busy at home with baby and mother, before a busy period of motor racing next month.
He will drive a Ferrari in GT World Challenge Australia at Phillip Island on April 12-14, then his Mobil 1 Optus Mustang Supercar at Taupo a week later.