Linea nigra: When does the pregnant belly line appear and why

Hello some one told me this line was a linea nigra which I've read

Dark line on your pregnant belly is the linea nigra, sometimes

Linea negra: a few words about the dark line on the belly during

The linea nigra (also called the pregnancy line) is a dark

Linea Nigra: What It Is, Causes And How To Get Rid Of It - MomJunction

Linea nigra

Linea nigra – the dark pregnancy line on my belly bump

Linea nigra: photos