Nuchal Translucency

Definition: NT refers to a small, thin hypoechoic space seen in the posterior fetal neck during the first trimester ultrasound. NT is a normal structure where size measurement is used as a risk factor for genetic disorders.

Significance: Enlarged NT(≥ 3.5 mm ) is associated with an increased risk of anatomic abnormalities (especially cardiac anomalies), chromosomal and genetic abnormalities (such as Down syndrome), and other adverse outcomes.

Cystic Hygroma

Definition: Cystic hygroma is usually seen as a large single or multilocular fluid-filled cavity located in the nuchal region, behind and around the fetal neck, which can extend the length of the fetus and can be seen on 1st trimester fetal ultrasound.

Cause: It often results from abnormalities in the lymphatic system.

Differentiation: Cystic hygroma is not a normal structure. It is usually larger than 3.5 mm (definition of enlarged NT), but occasionally it is difficult to differentiate a cystic hygroma from an enlarged NT, when there are septations seen.

Significance: It has a higher risk for aneuploidy, cardiac anomalies and fetal demise when compared to NT. 

Nuchal Fold

Definition: The nuchal fold is a normal fold of skin observed at the back of the fetal neck during the second trimester of pregnancy.

Measurement: The nuchal fold (NF) thickness is the distance from the outer edge of the occipital bone to the outer edge of the skin in axial section through the head at the level of the thalami, cavum septi pellucidi, and cerebellar hemispheres.

Significance: Increased thickness of the nuchal fold (≥ 6mm between 15 and 20 weeks of gestation) is considered a soft marker for Trisomy 21.

May 3, 2024

Key facts about dating a pregnancy using Crown-Rump Length 

• First trimester crown−rump length (CRL) is the best parameter for determination of gestational age in all pregnancies except those conceived by in vitro fertilization, which should be based on fertilization date.   
• The earliest ultrasound with a crown−rump length equivalent to at least 7 weeks (or 10 mm) shall be used to determine the gestational age¹.   
• Based on the Southern Ontario Obstetrical Network Consensus statement, the CRL Chart published by Daya et al.² shall be used for determination of gestational age.  

 

October 12, 2023

The nuchal translucency ultrasound - what it means for pregnant individuals

The power of this specialized ultrasound is explained by surgeon/sonologist Dr Mathew Lenoardi in an article for Empowering Women's Health. Please note that the timeframe for the nuchal translucency ultrasound is 11 weeks 2 days to 13 weeks 3 days, not 11 weeks 5 days to 13 weeks 6 days as indicated in the article. 

Sept 18, 2023
Get proof of registration for employment

Many employers now request that sonographers are registered in the NTQA program. The statement  "As of today’s date, dd-mmm-yyyy, Sonographer code XXXXX is currently registered as an active Nuchal Translucency Sonographer by the Ontario Multiple Marker Screening (MMS) Laboratories." has been added to the individual NT curve of active sonographers. Log into BIS, review your personalized NT performance distribution curve and take a screenshot to provide proof of registration to employers.