Looks like Ethel was a twin?
Births, December qtr 1917
Wolverhampton district     vol 6b, page 892
Swatman, Ethel D     Mother's maiden name: Preston
Swatman, Arthur      Mother's maiden name: Preston
Deaths, March qtr 1918
Wolverhampton district     vol 6b, page 708
Swatman, Arthur     age 0