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What is Twin peak sign on obstetric ultrasound indicates the presence of and explain in detail?
(A) Dichorionic 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, monochorionic-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 membrane and 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).> "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.