Impregnado literally means 'impregnated' or 'permeated'. While it can refer to biological impregnation, in this context, it's used to describe something thoroughly saturated or infused with a scent or presence.
In the song, the singer tells the 'thief' to take the car that is "impregnado com o perfume que ela usava" (permeated with the perfume she used). It's a vivid and somewhat dramatic word choice that emphasizes how deeply the ex-lover's scent lingers, making the car a painful reminder of the past.
Naiara Azevedo's "Ladrão" is such a clever and funny take on a breakup! The singer is being robbed, but instead of being scared, he sees it as an opportunity to get rid of everything that reminds him of his ex. He tells the thief, "Calma aí, não precisa me machucar não" [Hold on, you don't need to hurt me] and even says, "Não é um assalto, 'cê 'tá me fazendo é um favor" [It's not a robbery, you're doing me a favor].
He wants the thief to take the car that's "impregnado com o perfume que ela usava" [impregnated with the perfume she used] and even his wedding ring, saying "pra mim não vale nada" [it's worth nothing to me]. But the most important thing he wants stolen? His cell phone! He knows if he drinks, he'll want to call her, "Chorando, implorando pra voltar" [Crying, begging to come back]. He even adds, "Ainda bem que eu não sei o número dela de cor" [It's a good thing I don't know her number by heart]. It's a hilarious and relatable look at trying to move on from a past love.