Ultrasound Screening: Soft Markers & Anomalies Part 1 Flashcards
What is a vital time point for the 1st trimester ultrasound?
11 weeks
Many structures can’t be seen before then.
What is the normal limit for nuchal translucency (NT)?
Less than or equal to 3 mm
What measurement is increased nuchal translucency (NT)?
Greater than 3 mm
What are the risks associated with increased nuchal translucency (NT)?
aneuploidy (40%)–> example: Tris21
isolated cardiac defect (10%)
segmental aneuploidy (5%)
genetic cause that isn’t chromosomal (5%) ex: Noonan syndrome
segmental aneuploidy = gain or loss of chromosomal segment
About half = normal variation
What is the difference between nuchal translucency (NT) and cystic hygroma?
cystic hygroma has loculated cysts
loculated = bubbles or pockets of fluid
What risks are assocaited with cystic hygroma?
- aneuploidy (50%) esp Turner Syndrome (45, XO) and Trisomy 21
- cardiac defects, non-chromosomal genetic conditions
- fetal hydrops
- fetal death in utero (FDIU)
Cystic hygroma–>hydrops–>FDIU
Ultrasound soft fluid markers from least to most risk
(least) NT -> cystic hygroma -> fetal hydrops (most)
What are hydrops?
2+ abnormal fluid collections & generalized skin edema
(can be fluid in serous cavities: ascites (abdominal fluid), pleural effusions (fluid between lungs & chest), pericardial effusions (extra fluid around the heart)
What are the rates of mortality associated with hydrops?
perinatal mortality = 50-98%
liveborn infants = 48% w/in 1 year
What factors affect prognosis of a fetus with the finding of hydrops?
- etiology
- GA at onset
- GA at birth
- pleural effusions at birth or not
What are the 2 main findings related to hydrops with the worst prognosis and what can these findings lead to?
Especially prior to 20 weeks
- pleural effusions
- polyhydramnios (too much amniotic fluid)
- these can lead to pulmonary hypoplasia (incomplete development of the lungs) and preterm rupture of membranes/preterm at birth
earlier than later = bad
extra fluid = bad
hydrops + no aneuploidy + no major structural abnormalities =
better prognosis
What screening/testing do we offer for US finding at 11-14 weeks of increased NT and/or cystic hygroma?
- whole chromosome aneuploidy
- segmental aneuploidy
- fetal echo at 20 weeks
- eventually maybe single-gene testing if applicable
NIPT,CVS,Amnio
What is the major risk to pregnant person if fetal hydrops is found?
Mirror syndrome
What is mirror syndrome?
- generalized maternal edema
- pulmonary involvement mirror fetus
How can mirror syndrome present in a patient?
- rapid weight gain
- increasing peripheral edema
- progressive shortness of breath
- preeclampsia with severe symptoms
What is the solution for mirror syndrome?
delivery
fetus may not be viable
What is the increased risk for the USG finding of absent or hypoplastic nasal bone in the 1st or 2nd trimester?
trisomy 21
important note: hypoplastic/absent nasal bone is a normal variant in some people, especially in those of Afro-carribean or Asian decent
2nd note: It is not a birth defect.
What screening/testing should we offer for the finding of absent/hypoplastic nasal bone on US?
- best option in this scenario: NIPT
- first trimester screen (as long as lab doesn’t include absent nasal bone in calculations)
- CVS or amnio for diagnostic testing
What is omphalocele?
birth defect of the abdominal wall
intestines, liver, and other organs stick outside of the belly through the belly button
(gut spilling out)
What testing is appropriate for US finding of NT/cystic hygroma/hydrops?
- NIPT/cfDNA (PPV depends on condition, but is highest for Downs)
- CVS or amnio
- Maternal serum screening/1st trimester screening is NOT an appropriate option
positive NIPT + US finding = very likely to be true positive
NIPT–>CVS/Amnio
What is gastroschisis?
birth defect
a hole in the abdomen other than the belly button that allows the baby’s intestines to extend outside of the baby’s body
What time point must pass before a ventral wall defect can be diagnosed on US?
12-13 weeks gestational age b/c before this time it is normal for the gut to herniate in to the umbilical cord and then come back in later in deveopment, so if this is seen before 12-13 weeks it wouldn’t be considered a true ventral wall defect
What is a ventral wall defect?
gastroschisis or omphalocele as well as some other more rare defects
What should be offered for an omphalocele seen on US at 11 weeks?
Return to clinic in 2 weeks to re-assess by ultrasound.
Could also offer FTS or NIPT
What options are there for any other suspected major anomalies?
- FTS (not a great option for when an anomaly of any kind is found, but technically is an option)
- NIPT
- CVS or amnio
