Detailed scan.. worried 1st time mum.. help!

detailed scan at 20wk they found extra artery, shld have 3 but now have 4 but 1 which is not in use at baby heart which should be dissolve slowly when baby grow. Specialist advice some dissolve abit slow then others.. anyone experience this can share any tips or Any advice pls.. #pleasehelp #1stimemom #advicepls