A pregnant woman says she feels unsafe in her own home after her family was held up with a "giant knife" in a violent carjacking in Melbourne's west.

The woman, who doesn't want to be named, said she desperately grabbed her two-year-old child as her partner handed over the keys during the armed carjacking in Essendon on Saturday morning.

Catherine* and her family had just arrived home from breakfast about 11.15am when a large, Caucasian man approached their car.

Her partner complied, but their two-year-old child and dog were still in the car.

“He was pointing this giant knife at my partner and demanding he give him the keys,” Catherine told The Age.