TEALE FENNING

bluesky · Joined: 20 Sep 2008 Posts: 49

Would somebody be kind enough to explain how do we determine chorionicity of twins. I mean the lambda sign and twin peak sign and their significance.

rpwalavalkar · Teale Fenning Administrator Joined: 20 Jul 2006 Posts: 973

Lambda sign / Twin Peak sign

seen in Dichorionic twins where the babies have separate placentae, each will have an amnion and a chorion, so the membranes between them will be four layers thick and easy to see on scan. a moderately echogenic triangular shape where the placentae meet will be seen on scan, this looks like the 11th alphabet of the greek script hence called the Lambda sign.

Inverted T sign
When twins are monochorionic they share a placenta and have just the amnions between them, the membrane will appear very thin and there will be a T shape where the membranes meet the placenta.

Half Twin Peak Sign

separate placenta are associated with a triangular but more sharply tapered junctional area, also seen in dichorionic twins.

hope this helps.

R
_________________
Dr Miss. Raj Walavalkar MBBS MRCOG
TealeFenning Administrator
SR O&G Wessex Region