Abdominal Radiology

, Volume 43, Issue 7, pp 1841–1841 | Cite as

The lambda (twin peak) sign

  • Tsun Wai Jeffrey Wu
  • Yan-Lin LiEmail author
  • Kin-Hoi Wong
Classics in Abdominal Imaging
The lambda sign refers to the triangular projection of chorion between the layers of inter-twin membranes which resembles the Greek alphabet “lambda” (Fig. 1). It is best observed between 10 and 14 weeks of gestation on pelvic sonography, and its presence is highly suggestive of dichorionic diamniotic (DCDA) twin pregnancy (Fig. 2). The fused dichorionic placenta also assumes the appearance of a mountain top between the twin gestational sacs; thus the metaphorical source of its alternate title, the “twin peak” sign (Fig. 3) [1].
Fig. 1

The eleventh lower-case Greek alphabet “lambda”

Fig. 2

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

Fig. 3

A peak [2]


Compliance with ethical standards


No funding was received for this study.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Informed consent

Statement of informed consent was not applicable since the manuscript does not contain any patient data.


  1. 1.
    Sepulveda W, Sebire NJ, Hughes K, Odibo A, Nicolaides KH (1996) The lambda sign at 10–14 weeks of gestation as a predictor of chorionicity in twin pregnancies. Ultrasound Obstet Gynecol 7:421–423. doi: 10.1046/j.1469-0705.1996.07060421.x CrossRefPubMedGoogle Scholar
  2. 2.
    Photo courtesy of free-photos. Accessed 1 Oct 17

Copyright information

© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  1. 1.Li Ka Shing Faculty of MedicineUniversity of Hong KongHong KongChina
  2. 2.Department of Radiology, Queen Mary HospitalUniversity of Hong KongHong KongChina

Personalised recommendations