"Roberts sign refers to the presence of a gas shadow within the heart or the greater vessels, in cases of fetal death in utero. It is a rare sign caused by postmortem blood degeneration, usually seen 1-2 days after death; and may be seen as early as 12 hours."
"First described as a sign on radiographs by J B Roberts in 1944 1; it was first described on ultrasound in 1983 by Barbara J Weinstein, American radiologist and Lawrence D Platt, American obstetrician 2."
"History and etymology"