early linea nigra

Hannah • 5 beautiful children 14 angel babies pregnant and shooting for #6: the last one
Is it possible to start showing the line at 4 weeks? I got my BFP at 7 dpo so I have know for a week now. I went to the bathroom and happened to notice out of the corner of my eye the line which I didn't think came til middle of pregnancy. I have had children before does that make me prone to having the line?