Silly question...

Sarah • Im married with 3 lovely girls and my husband and i have decided to try for baby number 4.

So im asking for my sister in law as ive never had this..

The last time she had sex was last monday, today shes had spotting (just once when she wiped) could this be implantation or is it to far gone for that?? Or could it be something else??

Advice please xx