LAUSR

Sonograms at 5–6 weeks of gestational age depict the embryo as a focal thickening at the periphery of the yolk sac—an appearance referred to as ‘‘diamond ring’’ sign (Fig. 1) [1]. The yolk sac represents the ‘‘ring’’ and the embryo represents the ‘‘diamond’’ in this earliest sign of embryonic development [2, 3]. Just as an empty gestational sac measuring 25 mm or larger is highly specific for early pregnancy failure [3], absence of an embryo or the diamond ring sign in a gestational sac of 20 mm is worrisome for anembryonic gestation or early pregnancy failure [2, 3]. Gestational sac of mean sac dimension >25 mm without embryo or diamond ring sign and embryo of >7 mm with no cardiac activity have specificity and positive predictive value of 100% [4].