An orphaned premature baby whose parents were killed in a car crash last week has passed away on the day of her parents' funeral.

Lucy Schollbach was born 12 weeks premature on September 1.

Weighing only 1.3 kilograms, she was living in a humidicrib in the neonatal ward at the Royal Hospital for Women in the eastern Sydney suburb of Randwick, where her parents visited her twice a day.

But on Tuesday of last week, her parents - Justin Schollbach, 42, and Leah James, 33 - died in a car crash near their home at Kurnell while driving home from the hospital.