Flashcards in Prenatal diagnosis Deck (51)
What is an EIF and how commonly do they occur?
An EIF is a small echogenic area appearing within the fetal cardiac ventricle that has a sonographic brightness equivalent to that of bone, believed to represent a microcalcification of the papillary muscle. present a microcalcification of the papillary muscle. An EIF is a common finding during a routine second-trimester fetal anatomic survey and is identified in 3% to 5% of normal fetuses. The prevalence of EIF may vary according to maternal ethnicity (30% of fetuses of Asian mothers in one study).
What are the clinical implications of an isolated EIF?
An EIF is not considered a structural or functional cardiac abnormality. It has not been associated with cardiac malformations in the fetus or newborn. The only reported clinical implication is an increased risk of trisomy 21.When an EIF is identified, an experienced provider should perform a detailed fetal anatomic survey to assess for the presence of structural malformations and other sonographic markers of aneuploidy. In addition, the physician should perform an assessment of other risk factors, including maternal age, results of other screening or diagnostic tests, and family history. Most EIFs are isolated and occur in otherwise low-risk pregnancies.
When an isolated EIF is detected, how does counseling differ for women at increased risk for fetal aneuploidy and for women with normal aneuploidy screening results?
All patients, regardless of ultrasound findings, should be offered prenatal screening for aneuploidy and should have the option of invasive diagnostic testing. Counseling for a woman after prenatal identification of EIF should be guided by presence of other sonographic markers or structural abnormalities, maternal serum screening for risk of Down syndrome (if performed), and maternal age. If an isolated EIF is detected in a woman who has already had an invasive diagnostic testÌ¢‰âÂ‰Ûand the fetal karyotype is knownÌ¢‰âÂ‰Ûshe can be reassured that the finding is considered a normal variant.
What is the association between EIF and T21?
Meta-analyses - risk of trisomy 21 was increased 1.8- to 5.4-fold by the finding of an isolated EIF. Recently, another meta-analysis similarly identified a 2.9 likelihood ratio (LR) for isolated EIF, when defined as no major abnormalities and no evidence of ventriculomegaly, increased nuchal skinfold thickness, echogenic bowel, pyelectasis, short humerus, or short femur.
How should a woman with an isolated EIF be followed throughout pregnancy?
Because an isolated EIF does not represent a cardiac abnormality, fetal echocardiography is not needed and no specific follow-up is recommended. Follow-up should be performed based on the presence of other clinical indications or the results of the patientÌ¢‰âÂ‰ã¢s prenatal screening and/or diagnostic testing.
What are the ultrasound features of triploidy?
Placental abnormalities of hyditaform degeneration are present in almost all cases in which the extra haploid set of chromosomes are paternal but much less common if maternal.
The placenta may appear thickened or demonstrate cystic changes on U/S but these changes are variable. Common fetal features include holoprosencephaly and hydrocephalus (50%), agenesis of the CC, NTD (25%), facial abnormalities (low set ears, micrognathia, cleft palate), IUGR/small abdomen, single umbilical artery, syndactyly of the 3rd and 4th fingers, cardiac anomalies (60%), GU anomalies.
What are the differences between Type I and Type II triploidy?
Type I is paternal with a large cystic placenta, symmetric IUGR, elevated maternal hCG, AFP and inhibin.
Type II is maternal with small non-cystic placenta, low levels of hCG and estriol.
What does this karyotype mean: 45XX -14,-21, +t(14,21)?
Robertsonian translocation, present in about 4 percent of Down syndrome patients.
Translocation is usually between 21q and another acrocentric chromosome - usually 14 and 22.
A carrier involving 14 and 21 has only 45 chromosomes - one chr 14 and one chr 21 are missing, and are replaced by the translocation chromosome t(14q21q).
6 possible types of gametes, 3 are nonviable, 1 is normal one, is balanced and 1 is unbalanced (has both chr 21 and the translocated chromosome).
15 percent of progeny of mothers are affected. Less if father is affected.
What genetic abnormalities are associated with advanced paternal age?
Achondroplasia, thanatophoric dysplaisa, OI, Marfan's
T21 - NT, PAPP-A, f-BhCG
Incr NT, low PAPP-A, high BhCG(Median MoM - PAPP-AP 0.38, BhCG 1.83)
T18 - NT, PAPP-A, f-BhCG
Incr NT, low PAPP-A, low BhCG
Pregnancy loss < 24w
Incr NT, very low PAPP-A, very low BhCG
Congenital heart defect
Incr NT, normal PAPP-A, normal BhCG
Most powerful marker for general population screening for T21
When can NT be performed?
Between 10 3/7 and 13 6/7 weeks gestationCRL 36 - 84 mm
Criteria for NT measurement
1. Fetus in midsagittal plane, ideally with spine down2. Only fetal head, neck, and upper thorax fill the viewable area3. Fetal neck should be neutral - not hyperflexed or hyperextended4. Skin at the fetal back clearly differentiated from underlying amniotic membrane5. Measurement calipers placed on inner borders of echolucent space, perpendicular to long axis of fetus6. US and transducer setting optimized to ensure clarity of the image and borders of NT. May require TVUS
FASTER trial results for NT sonography
Multicenter prospective trial36,306 pts from general population had 1st trimester NT sonoDetection rate 70% at 11w, 64% at 13w, for a 5% false + rate
Sensitivity of BhCG + PAPP-A + maternal age for T21
60% with a 5% FP rate
Sensitivity of NT + BhCG + PAPP-A + maternal age for T21 (FASTER)
11w - 87%12w - 85%13w - 82%(5% FP rate)
Does 1st trimester combined screening have a significantly better performance than 2nd trimester quad for T21?
Only when performed at 11w - 87% vs 81%, at 5% FP
Which test has the lowest false + rate for T21 - 1st trimester combined or quad?
1st trimester combined
What is a septated cystic hygroma?
The NT space is enlarged, extending along the entire length of the fetus, and septations are clearly visible
Risk of fetal aneuploidy with septated cystic hygroma? Which ones?
50%Most cases T21, then 45,X and T18
Among euploid cystic hygroma cases, risk of major structural fetal malformation? Which ones?
50%Most cases cardiac abnl, also skeletal dysplasia
Risk of fetal malformation or demise with septated cystic hygroma vs simple incr NT
Septated CH - 5x more aneuploid, 12x more cardiac abnl, 6x more fetal or neonatal demise
If a simple NT >/= ___ is noted, then CVS should be offered bc the minimum risk of aneuploidy is 1 in 6
NT >/= 3 mm
Percent of T21 fetuses w/ nonvisualization of the nasal bone (Cicero 2001)
70% (43/59), vs 0.5% of unaffected fetuses (3/603)
Sensitivity of NB + NT + BhCG + PAPP-A + maternal age for T21
85% for 1% FP rate in Cicero 200167% for 2.8% FP rate in Cicero 2003
Technique for imaging nasal bone
1. Midsagittal plane with perfect fetal profile2. Fetal spine posterior, slight neck flexion3. 2 echogenic lines - superficial is nasal skin, deeper is nasal bones4. Deeper echogenic line representing nasal bone should be more echolucent at its distal end5. Care taken not to have US beam parallel to plane of NB - may appear absent