Russell-Silver syndrome: an explanation for discordant growth in monozygotic twins.

Severe intrauterine growth retardation and suggestive dysmorphic and malformation syndrome in 1 twin with a normal karyotype during a monozygotic, monochorionic pregnancy led to the diagnosis of discordant Russell-Silver syndrome (RSS). Placental anomalies (velamentous cord insertion, single umbilical artery, placental hypotrophy) for the small-for-date twins and a twin-twin transfusion syndrome confirmed at 21 weeks of amenorrhea suggest that early hemodynamic disorders may reveal or trigger RSS which has been considered to be of genetic origin. The prognosis for RSS is favorable, except for diminished adult size (less than -2 standard deviations).