White lambda and black lambda in obstetric ultrasound of twin gestation =====

White lambda and black lambda in obstetric ultrasound of twin gestation =====

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In dichorionic diamniotic twin pregnancy, there is a triangular projection of placental tissue which extends from the placenta between the layers of amniotic and chorionic membranes of each fetus.

This ultrasound finding is called “lambda” or “twin peak” sign.

With advancing gestational age, there is regression of the chorion laeve and the lambda sign becomes difficult to identify. Thus by 20 weeks only 85% of dichorionic pregnancies demonstrate this sign.

In monochorionic diamniotic twin pregnancy

It’s called t sign

بص علي اول صوره

the inter-twin membrane consists only of the two layers of amnion.

بص علي خامس صوره

In DCDA it’s a 4 layered membrane

بص علي رابع صوره

The chorionic tissue within the septum is missing. The ultrasound examination shows so called “T” sign at the placental side.

بص الفرق بين الاتنين في أول صوره

Furthermore, in-utero two thin walled amniotic sacs can be seen creating a black triangular space between the outline of the amniotic sacs and the uterine wall and/or chorion in the extraembryonal coeloma called the “black lambda” sign.

بص علي صوره ٦ و ٧

This “black lambda” sign is present at monochorionic twin pregnancies and should not be confused with the ambda (white lambda)which is a characteristic sign for dichorionic twins.

بص علي تاني صوره

لوغاريتم ال twin ultrasound

في تالت صوره

لو استفدت اعمل شير