Blood gender tests after recently having a baby!

Angela

My neighbor recently had her little boy and is now pregnant again, 3 months later. So technically like 2 months after giving birth.. she’s having a blood gender test done at a local ultrasound place but it got me thinking.. how accurate could it be that soon after giving birth? She’s getting it done at 9 weeks.. I think it might tell her she’s having another boy even if it’s a girl just because she had a boy so recently.

What do you think?