SOFT MARKERS IN US ANOMALY SCAN

Dr.Ghalandarpoor Assistant professor TUMS INTRODUCTION

• Approximately 3 percent of live births are affected by a major structural malformation *With advances in prenatal ultrasound, many of these anomalies are now identified before birth. The etiology is diverse and includes environmental factors, genetic factors, or a combination of both. • As the landscape of genetic testing rapidly evolves, clinicians are often left with many questions about the most appropriate testing methods to use for their patients. FREQUENCY OF CHROMOSOME ABNORMALITIES

• The finding of a fetal structural anomaly increases the possibility of a chromosome abnormality or genetic molecular defect • should prompt further evaluation into genetic etiologies. The frequency of a chromosome abnormality depends on the specific anomaly, the number of anomalies, and the combination of anomalies identified • In several retrospective series of prenatally detected anomalies on ultrasound that prompted genetic studies, an isolated fetal anomaly was associated with fetal chromosome abnormalities in 2 to 18 percent of cases; multiple anomalies were associated with a fetal chromosome abnormality in 13 to 35 percent of case • There are two types of fetal chromosomal abnormalities identifiable by karyotype and microarray: • , which is an abnormal number of chromosomes • Aberrations of chromosome structure, such as deletions, rings, translocations, and Duplications

Aneuploidy is the most common genetic abnormality detected by prenatal diagnosis • Of the 6006 fetal karyotypes obtained at one center,

151 of the 207 abnormalities (73 percent) were (trisomy, triploidy, monosomy), and about 90 percent of these involved chromosomes 21, 18, 13, X, or Y (135/207 or 65 percent of all karyotypic abnormalities) • Fetal chromosomal abnormalities are more common in the first and second trimesters than in live born infants, due to the high rate of spontaneous loss of these over the course of • Termination of affected also plays a role. THE ANTEPARTUM DETECTION OF FETAL ANEUPLOIDY IS ONE OF THE MAJOR GOALS OF PRENATAL SCREENING PROGRAMS

• Sonographic examination is useful • fetuses with abnormal karyotypes often have anatomic changes or anomalies. • Sonographic findings, results of maternal cell-free DNA or biochemical marker screening, and parental risk factors for genetic disease are all considered in determining the risk that the is affected. • However, invasive testing ( or chorionic villus biopsy) is required to obtain a definitive karyotypic diagnosis. ULTRASOUND MARKERS

• Soft markers are ultrasound findings of uncertain significance • They are often associated with normal fetuses (ie, normal variants), usually have no clinical sequelae, and are transient, resolving with advancing gestation or after birth. • They do carry an increased risk for fetal aneuploidy, however, and correlation with the patient's biochemical risk status should be done SOFT MARKERS

• Increased nuchal translucency • Absent nasal bone • Echogenic bowel • Pyelectasis • Shortened long bones (humerus, femur) • Echogenic intracardiac focus • Choroid plexus cysts • Isolated soft markers are identified in 11 to 17 percent of normal fetuses • prevalence is higher in aneuploid fetuses and the likelihood of aneuploidy is significantly increased when more than one marker is present • Even in this setting, use of soft markers for screening for, or excluding, fetal aneuploidy is inefficient; however,

• a detailed evaluation of fetal anatomy should be performed whenever one or more soft markers has been identified. • Screening for soft markers is not a component of a basic obstetrical ultrasound examination. • Detection and reporting of soft markers (ie, echogenic intracardiac focus and choroid plexus cysts) is controversial because this information is anxiety- provoking for patients, requires considerable time for counseling, and may lead to invasive . • Such testing may result in procedure-related loss of a normal fetus, and is costly. SOCIETY FOR MATERNAL-FETAL MEDICINE PROVIDES THE FOLLOWING GUIDANCE

• For women who undergo cell-free DNA screening, ultrasound solely to assess nuchal translucency at 11 to 14 weeks is not recommended.

• An isolated soft marker is not considered a marker for aneuploidy if the cell- free DNA screen or first- or second-trimester biochemical screen is negative. However, some soft markers may have clinical implications (eg, echogenic bowel may be associated with cystic fibrosis; pyelectasis may be associated with vesicoureteral reflux).

• All women with a fetal structural abnormality on ultrasound should be offered diagnostic testing with chromosomal microarray.

SECOND TRIMESTER NUCHAL FOLD

• The nuchal fold is the measurement between the outer edge of the occipital bone to the outer margin of the skin and is taken in the axial plane. • An increase in this measurement is also associated with aneuploidy. An increased nuchal fold is detected in 20 to 33 percent of fetuses with Down syndrome and 0.5 to 2 percent of euploid fetuses • LR:11-17;may decreases over gestation SECOND TRIMESTER ABSENT NASAL BONE • the reported sensitivity of absent nasal bone for Down syndrome varies widely, but is generally lower than in the first trimester • The nasal bone is absent in about 30 to 40 percent of Down syndrome fetuses and 0.3 to 0.7 percent of euploid fetuses.it is hypoplastic in about 50 to 60 percent of Down syndrome fetuses and 6 to 7 percent of euploid fetuses. • Affected by race and ethnicity • Using either nasal hypoplasia or absence as a marker increases sensitivity, but also the false positive rate. Options include: * the ratio of biparietal diameter-nasal bone length (BPD/NB thresholds of >9 to >12 *a single pre-defined threshold for abnormal nasal bone length (≤2.5 mm), *a -based threshold (<2.5th or 5th centile) based on the distribution of nasal bone length in normal fetuses, or *use of multiple of the median(MoM) of nasal bone length for gestational age (<0.75 MoM). In a systematic review, the MoM method appeared to have the best combination of sensitivity and specificity (54 and 94 percent, respectively ECHOGENIC BOWEL

• It may be first identified in the first trimester but is more commonly identified in the second trimester.

• It has been found in 1 to 2 percent of normal fetuses and 13 to 21 percent of fetuses with Down syndrome. However, a variety of fetal and pregnancy complications have also been associated with this finding: other chromosomal defects, fetal growth restriction,cystic fibrosis, congenital infection, intraamniotic bleeding, and gastrointestinal obstruction

• Aneuploidy has been associated with abnormal bowel function (decreased motility, increased water absorption) in newborns and it is possible that a similar process in the fetus could cause echogenic bowel PYELECTASIS • Pyelectasis or mild hydronephrosis is a common finding in fetuses. • diameter of ≥4 mm at 15 to 19 weeks of gestation demonstrated pyelectasis in 10 to 25% of fetuses with Down syndrome and 1 to 3 % of euploid fetuses. • Aneuploidy is present in 0.3 to 0.9% of fetuses with isolated pyelectasis • When pyelectasis is identified in an otherwise normal second trimester fetus, a normal cell-free DNA test for fetal aneuploidy can be very reassuring and obviate the need for invasive testing • In both euploid and aneuploid fetuses, pyelectasis is usually caused by vesicoureteral reflux, but may be related to obstruction. • Mild dilation (ie, 4 to 7 mm in the second trimester) typically resolves over the course of gestation or in the postnatal period

VENTRICULOMEGALY

• Isolated ventriculomegaly is a risk factor for Down syndrome, • Most children with isolated, mild ventriculomegaly have a normal outcome.

• Mild ventriculomegaly is detected in 4 to 13% of fetuses with Down syndrome and 0.1 to 0.4% of euploid fetuses .

• The risk of abnormal outcome, such as Down syndrome, increases with the degree of ventriculomegaly, progression of ventriculomegaly, and presence of other anomalies

SHORTENED LONG BONES

• Fetuses with Down syndrome have slightly shorter long-bones. A shortened humerus appears to be a better predictor of Down syndrome than a shortened femur (positive likelihood ratio 4.8 and 3.7, respectively) • Various criteria have been published for determining whether a femur or humerus is too short .These criteria overlap the range observed in unaffected fetuses and vary widely among different populations; • therefore, each laboratory should develop specific standards for its own population. We consider abnormal an observed-to-expected length ratio of less than 0.9. • In contrast, severely shortened (<5th percentile) or abnormal appearing long bones may be a sign of a skeletal dysplasia or early onset fetal growth restriction ECHOGENIC INTRACARDIAC FOCUS

• The sonographic criteria for echogenic intracardiac foci is brightness equivalent to that of bone. • Echogenic intracardiac foci usually occur as a single focus in the left ventricle, but multiple foci, biventricular foci, or a right ventricular location can also occur. • This entity is different from diffuse, extensive myocardial calcification, which is rare and associated with myocardial dysfunction • Echogenic intracardiac foci may be first identified in the first trimester, but identification this • early in pregnancy is rare. In the second trimester, 21 to 28 % of fetuses with Down syndrome have an echogenic intracardiac focus, while this is seen in 3 to 5 %of normals

• The incidence varies across races/ethnicities (present in up to 30 percent of • Asian fetuses), and decreases with advancing gestational age. • It is thought to be related to microcalcification and fibrosis of the papillary muscle or chordae, often disappears later in pregnancy or postnatally, and is not associated with myocardial dysfunction or structural anomalies • In an autopsy study of abortuses, stillbirths, and perinatal deaths, discrete central papillary muscle calcification was more common in fetuses with trisomy 13 than trisomy 21 • The best available evidence suggests that an isolated echogenic intracardiac focus in the fetus of an otherwise low risk woman does not confer an increased risk of fetal aneuploidy

• Although some studies have reported that the number or location of echogenic foci affects the risk of fetal aneuploidy (higher risk with biventricular or right ventricular involvement), the general consensus is that these factors have not been proven to matter

• When an echogenic intracardiac focus is identified in an otherwise normal second trimester fetus, a normal cell-free DNA test can be very reassuring and obviate the need for invasive testing CHOROID PLEXUS CYSTS

• They may be visualized during the late first trimester, but their prevalence has not been determined this early in pregnancy. They usually disappear by the third trimester; those that persist are usually asymptomatic and benign. • They appear to result from filling of the neuroepithelial folds with cerebrospinal fluid • The typical sonographic appearance is a small (usually less than 1 cm), sonolucent structure(s) with well delineated borders located within the choroid plexus. A wide range of appearances are possible from unilateral single cysts to bilateral septated and multiple cysts A targeted scan for other fetal anomalies should follow imaging of these cysts. • Choroid plexus cysts are present in 30 to 50 % of fetuses with trisomy 18 compared with 0.6 to 3 %t of all second trimester fetuses. *choroid plexus cyst(s) with an otherwise completely normal detailed structural survey (including examination of the face, heart, great vessels, and extremities) is highly reassuring of a normal karyotype .In addition, • if the fetus is able to unclench its hand and hold it open, trisomy 18 is not likely. • When isolated choroid plexus cyst(s) are detected in an otherwise low risk patient the risk of amniocentesis (1/250 chance of pregnancy loss) is higher than the risk that the fetus has trisomy 18 (less than 1/374). • We suggested restricting amniocentesis to patients with additional sonographic abnormalities or high risk factors (ie, advanced maternal age [older than 32 years at deliver], abnormal serum analyte screen) . Some women may request amniocentesis after risk-benefit counseling. When choroid plexus cysts are identified in an otherwise normal second- trimester fetus, a normal cell-free DNA test can be very reassuring and obviate the need for invasive testing OTHER

• Although more prevalent in patients with Down syndrome, sandal gap toe, short ear length, and a hypoplastic wedge-shaped middle phalanx of the fifth digit that causes it to curve toward the fourth finger (clinodactyly), are also common normal variants • An observed-to-expected iliac length measurement ≥1.21 or a widened iliac angle (>90 degrees) has a low positive predictive value for the detection of Down syndrome in low risk populations • An aberrant right subclavian artery is more common in Down syndrome fetuses than euploid fetuses (prevalence 24 %t in Down syndrome versus about 1 percent in • screened obstetric populations), but it is usually not an isolated finding in Down syndrome SINGLE UMBILICAL ARTERY

• There is a well-documented association between single umbilical artery (SUA) and an increased risk of aneuploidy when additional fetal malformations are detected. • The rate of aneuploidy with isolated SUA is not known, but most experts do not recommend routine chromosomal analysis if there are no other malformations or other indications for genetic amniocentesis

FETUS WITH "SOFT MARKERS" AND NO STRUCTURAL ANOMALIES

• Soft markers detected before cell-free DNA or biochemical marker aneuploidy screening *For patients with two or more soft markers who decline invasive diagnostic testing but are interested in further evaluation, the authors offer cell-free DNA screening because this is the most sensitive single test for the common aneuploidies. If results from cell-free DNA screening show no increased risk for trisomy 21, 18, 13, or sex chromosome anomalies, then patients are offered reassurance and typically continue with routine . • However, as discussed previously, we always stress that a negative screening result does not eliminate the possibility of a genetic condition in the fetus. SOFT MARKERS DETECTED AFTER NEGATIVE CELL- FREE DNA OR BIOCHEMICAL MARKER ANEUPLOIDY SCREENING: • 1- Isolated soft marker • provide counseling and reassurance. Some isolated soft markers, such as thickened nuchal fold, absent nasal bone, and echogenic bowel, are more strongly associated with fetal aneuploidy. In such cases, additional genetic counseling and cell-free DNA screening may be warranted • Some soft markers in euploid fetuses are associated with specific disorders (eg, echogenic bowel has been associated with cystic fibrosis). • .Soft ultrasound findings that are likely normal variants in this setting include echogenic intracardiac focus,choroid plexus cyst, sandal gap toe, and clinodactyly. • 2- Two or more soft markers: genetic counseling SMFM GUIDANCE FOR: WOMEN WITH NEGATIVE CELL-FREE DNA SCREENING AND ISOLATED SOFT MARKER • recommends not offering diagnostic testing solely for the indication of an isolated soft marker when prior cell-free DNA screening was negative. We agree with the SMFM publication that an isolated soft marker should not be overemphasized in patients with negative cell-free DNA screening and that some soft markers should be described as a normal variant. • Some soft markers in euploid fetuses are associated with specific disorders or may warrant additional ultrasound evaluation/monitoring, which should be addressed during counseling. A false negative cfDNA is unlikely, but probably higher with these soft markers than with the normal variants described above. • These soft ultrasound findings include: pyelectasis, single umbilical artery, ventriculomegaly, echogenic bowel, thick nuchal fold, absent nasal bone, and shortened humerus or femur •As most soft markers resolve by the third trimester, we do not recommend postnatal genetic evaluation unless there are signs of aneuploidy on clinical examination. FOR PATIENTS WHO HAVE HAD NEGATIVE FIRST- OR SECOND-TRIMESTER BIOMARKER ANEUPLOIDY SCREENING FOLLOWED BY IDENTIFICATION OF: 1-An isolated soft marker – We provide counseling and reassurance. Some isolated soft markers, such as thickened nuchal fold, absent nasal bone, and echogenic bowel, are more strongly associated with fetal aneuploidy .In such cases, additional genetic counseling and cell-free DNA screening may be warranted Some soft markers in euploid fetuses are associated with specific disorders (eg, echogenic bowel has been associated with cystic fibrosis). 2-Two or more soft markers – We offer genetic counseling to discuss cell-free DNA screening and diagnostic testing options ANOMALOUS FETUS: DIAGNOSTIC APPROACH

• We offer a diagnostic procedure to patients with structural fetal abnormalities on ultrasound examination .The goal is to determine whether there is a genetic etiology of the abnormalities that would enable well- informed counseling about prognosis, reproductive options, obstetric and pediatric management, and recurrencerisks. • The decision to undergo invasive testing is personal and must be based on the individual patient's values and goals. Pretest counseling by a provider familiar with the suspected fetal diagnoses and with genetic testing options is necessary for patients to make informed decisions FOR AN ANOMALOUS FETUS WITH SONOGRAPHIC FEATURES CONSISTENT WITH A COMMON TRISOMY

• begin the genetic evaluation with interphase FISH for the major aneuploidies. • If the FISH is abnormal, the results should be confirmed with a G-banded karyotype in order to determine if the aneuploidy • detected is secondary to an unbalanced translocation (representing a risk for a balanced translocation in a parent) or nondisjunction • If the FISH is normal, we offer chromosomal microarray analysis as we believe this approach allows for the highest diagnostic yield. CMA can be performed on the same fetal specimen used for FISH. FOR AN ANOMALOUS FETUS WITH SONOGRAPHIC FEATURES THAT DO NOT PRIMARILY SUGGEST A COMMON TRISOMY

• begin the genetic evaluation with CMA. Our approach is the same whether the anomaly appears to be isolated or multiple structural anomalies are observed • an isolated anomaly still warrants a thorough investigation when desired by the patient. Furthermore, an apparently isolated anomaly on prenatal ultrasound may not be isolated when the newborn is evaluated POSTTEST COUNSELING

● Abnormal results: *Significance of results for the health of the fetus, before and after delivery, *Review patient's goals and values and pregnancy management options, as discussed during pretest counseling. *Recommended follow-up after delivery. *Review of recurrence risk and options for future pregnancies

● Normal results: *Discuss that while normal results are reassuring, they do not eliminate the possibility of an underlying genetic condition in the fetus. *Review options for additional evaluation after delivery, including consultation with a medical geneticist if appropriate • Down syndrome risk estimates derived from different sonographic prediction tools("genetic sonogram") can be quite discordant, even if they use the same ultrasound markers. • The use of cell-free DNA screening has replaced the genetic sonogram as a secondary screening test for women found to be at increased risk for Down syndrome on serum biochemical screening. Cell-free DNA screening is also offered to women with normal biochemical screening tests if ultrasound examination detects soft markers, thereby lowering the rate of false-negative biochemical screens and improving detection of affected fetuses.