Lambda (λ) sign in USG

Lambda (λ) sign

What is lambda sign?

  • Lambda sign refers to the triangular projection of chorion between the layers of inter-twin membranes which resembles the Greek alphabet “lambda”.

What is suggested by Lambda (λ) sign in USG?

  • Lambda (λ) sign in USG – Strongly suggests a dichorionic twin pregnancy.

Lambda (λ) sign in USG is best seen in which Trimester?

  • Best seen in the first trimester – between 10-14 weeks

What is the othername for Lambda (λ) sign in USG?

  • Twin peak sign is other name for lambda (λ) sign
  • Lambda (λ) sign is a useful indicator of dichorionicity

Ultrasound image of lambda sign in first trimester

ResearchGate. Available from: [accessed 12 Jan, 2023]

Source :

Transabdominal pelvic ultrasound image obtained at 16 weeks of gestation shows both foeti labeled A and B. The limbs of the lambda sign are highlighted with arrows. The ‘peak’ is labeled with an asterisk

USG First TrimesterIndicates
1T signMonochorionicity
2Lambda (λ) signDichorionicity
Lambda (λ) sign

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