Is Nipt accurate if you get pregnant shortly after birth

Not planning on getting pregnant right after this baby , but I want them to be about a year apart so I’ll probably start trying a few months later I’m thinking maybe 6 months later. But I’ve heard that fetal dna stays in the mother for a long time after birth. I’m having a boy now, so if I get pregnant later with a girl, will it be able to tell it’s a girl if the boy dna is possibly still lingering ?