Module 18 : Nuchal Lucency Flashcards
what is the incidence of chromosomal abnormalities increased with with NL
- size of NL rather than appearance
what is the window of opportunity to do a NL
- 11weeks - 13 6 days
- 45mm - 84mm
why do we have to start to NL at 11 weeks
- in a fetus with chromosomal abnormality the nuchal fluid begins to increase at 11 weeks
what other abnormalities can we see at the NL scan
- acrania
+ skull ossified around 11 weeks - ompalocele
+ normal up until 11 weeks
why end at 13 w 6 d
- in a fetus with a CA the nuchal fluid decreases after 14 weeks
how accurate is the nuchal scan what makes it more accurate
- very accurate
- with first trimester blood work is even more accurate
what can a this nuchal be indicative of
- chromosomal defect
- cardiovascular defect
- pulmonary defect
- skeletal dyplasia
- congenital infectious
- hematologic disorders
- metabolic disorders
protocol for measuring CRL
- measure with spine anterior or posterior
- midline sag plane
- do not use coronal plane
- fetus in neutral plane `
what are the 5 criteria for NL
- magnification
- positon
- amnion
- measurement area
- caliber placement
magnification
- only fetal head and thorax on image
- about only 3-4 cm of depth
position
- true sagittal on fetus \+ nasal bone an nuchal together - fetus in neutral position \+ hyperextension can create a 0.6mm increase \+ flexion can create a 0.4mm decrease \+ head turned increase NL as well
amnion
- fetus should be lifted off the amnion
measurement area
- measure widest portion the NT
- anywhere from the occiput to the thorax
calliper placement
- on to on
- only cross calipers
- cross hairs line up with top and bottom of membrane
what factors are part of the risk assessment
- maternal age
- CRL
- NT
- blood analysis
- fetal heart rate
what number is considered a positive risk for NT
> 1/300
what will give you a positive risk no matter what NT
- being over 40
- blood work can help make this a negative result
what things should we asses during NT scan
- heart rate
- cranium
- abdominal wall
- bladder
- stomach
- limbs
what is the protocol for NT with a nuchal cord
- nuchal measurement is the taken above or below nuchal cord than averaged
- use color doppler to confirm location
what should we assess with multiple gestation
- assess chronicity and amnionicity
- best time to visualize membranes
