'Twin peak" sign is seen in: (A) Dichorionic diamniotic twins, (B) Monochorionic monoamniotic twins, (C) Discordant twins, (D) Conjoined twins
Answer is A. (A) Dichorionic diamniotic twins # Twin peak sign indicates the presence of a dichorionic-diamniotic twin gestation. It represents the extension of placental villi into the potential space that is formed from the reflection of apposed amniotic and chorionic layers from each fetus.> By performing an obstetric ultrasound at a gestational age of 10-14 weeks, mono- chorionic-diamniotic twins are discerned from dichorionic twins.> Presence of a "T-sign" at the inter-twin membrane-placental junction is indicative of monochorionic-diamniotic twins (that is, the junction between the inter-twin membraneand the external rim forms a right angle), whereas dichorionic twins present with a "lambda (I) sign" (that is, the chorion forms a wedge-shaped protrusion into the inter-twin space, creating a rather curved junction).> The "Lambda sign" is also called the "twin peak sign".> At ultrasound at a gestational age of 16-20 weeks, the "lambda sign" is indicative of dichorionicity but its absence does not exclude it.