The double decidual sign is an ultrasound finding seen in very early intrauterine pregnancies, typically around 4 to 5 weeks of gestational age. It appears as two concentric echogenic rings surrounding the gestational sac, representing the decidua capsularis, which surrounds the sac, and the decidua parietalis, which lines the rest of the uterine cavity. This sign is important because it helps distinguish a true early intrauterine pregnancy from a pseudogestational sac, a small fluid collection that can sometimes be seen in the uterus when there is an ectopic pregnancy elsewhere. Identifying the double decidual sign provides reassurance that the pregnancy is properly implanted within the uterus.
Sonography Term