The sonographic detection of trisomies 13, 18, and 21

Clinically Relevant Prenatal Ultrasound Diagnosis of Umbilical Cord Pathology

Umbilical cord abnormalities are not rare, and are often associated with structural or chromosomal abnormalities, fetal intrauterine growth restriction, and poor pregnancy outcomes; the latter can be a result of prematurity, placentation deficiency or, implicitly, an increased index of cesarean delivery due to the presence of fetal distress, higher admission to neonatal intensive care, and increased prenatal mortality rates. Even if the incidence of velamentous insertion, vasa praevia and umbilical knots is low, these pathologies increase the fetal morbidity and mortality prenatally and intrapartum. There is a vast heterogeneity among societies’ guidelines regarding the umbilical cord examination. We consider the mandatory introduction of placental cord insertion examination in the first and second trimester to practice guidelines for fetal ultrasound scans. Moreover, during the mid-trimester scan, we recommend a transvaginal ultrasound and color Doppler assessment of the internal cervical os for low-lying placentas, marginal or velamentous cord insertion, and the evaluation of umbilical cord entanglement between the insertion sites whenever it is incidentally found. Based on the pathological description and the neonatal outcome reported for each entity, we conclude our descriptive review by establishing a new, clinically relevant classification of these umbilical cord anomalies.

High accuracy of quantitative fluorescence polymerase chain reaction combined with non-invasive pre-natal testing for mid-pregnancy diagnosis of common fetal aneuploidies: A single-center experience in China

Quantitative fluorescence polymerase chain reaction (QF-PCR) may be used as a mid-pregnancy test to confirm the diagnosis of common fetal aneuploidies, but its use is controversial. The present study aimed to determine the value of QF-PCR for diagnostic confirmation of karyotyping and the impact of parental origin and meiosis stage on the detected aneuploidy. The present prospective cohort study included pregnant women (age, 21-45 years; gestational age, 17-25 weeks) who consulted between May 2015 and December 2016. Women were screened and only consecutive high-risk individuals were included (n=428). QF-PCR analysis of amniocytes was performed. Karyotype analysis was considered the gold standard. Parental karyotyping was performed if the embryo exhibited any aneuploidy. GeneMapper 3.2 was used for data analysis. There were no false-negative or false-positive QF-PCR results, with 100% concordance with the karyotype. The aneuploidy distribution (n=105) was 68.6% for trisomy 21, 19.0% for trisomy 18, 7.6% for sex chromosome aneuploidy, 3.8% for trisomy 13 and 1.0% for 48,XXX,+18. Regarding trisomy 21, most cases (86.1%) were of maternal origin, 8.3% paternal and 6.5% undefined. Trisomy 18 was 88.2% maternal and 11.8% paternal. Maternal meiosis stage errors in trisomy 21 mainly occurred in meiosis I, while the origin of trisomy 18 exhibited similar proportions between meiosis I and II. The combination of non-invasive pre-natal testing and QF-PCR may become a rapid and effective method for fetal aneuploidy detection. QF-PCR may provide more genetic information for clinical diagnosis and treatment than karyotyping alone.

Update and Review: Maternal Serum Screening

Maternal serum levels of alpha fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE3) can be used to screen pregnancies for neural tube defects, Down syndrome, Trisomy 18, and pregnancy complications. This article summarizes the most recent information regarding maternal serum screening, including genetic counseling issues.

Second trimester ultrasound markers of fetal aneuploidy

Although it is widely accepted that the best time to screen for chromosomal abnormalities is the first trimester, ultrasound evaluation of the fetus in the second trimester has also been shown to be useful for this purpose. A multitude of markers of varying strength has been developed over the past 30 years. In addition, the optimal time to diagnose fetal anomalies with confidence is also the mid second trimester. Therefore, performance of obstetrical ultrasound at this point in gestation continues to be an important component of prenatal care.

Prenatal diagnosis of craniomaxillofacial malformations: a characterization of phenotypes in trisomies 13, 18, and 21 by ultrasound and pathology

OBJECTIVE

To determine the relationship between trisomies 13, 18, and 21 and craniofacial malformations detected by prenatal sonography.

DESIGN

During a 29-year period (1976 through 2004), prenatal sonographic findings of 69 fetuses with trisomy 13; 171 fetuses with trisomy 18; 302 fetuses with trisomy 21; and 17 fetuses with other trisomies were evaluated retrospectively, after fetal karyotype identification. Sonographic findings were compared with autopsy results in 209 patients (trisomy 13, n=39; trisomy 18, n=64; and trisomy 21, n=106).

RESULTS

For trisomy 13, cleft deformities were detected prenatally in 65.2%, and of the 39 cases with pathological information, 76.9% were found to have a cleft deformity. Ocular and orbital abnormalities were found in 28%. Malformations of the jaws and abnormal profiles were more frequently diagnosed postnatally than prenatally. For trisomy 18, abnormal profiles (41.5%) and ear abnormalities (5.3%) were the most noticeable ultrasound markers, next to abnormalities of the neurocranium (36.8%) and cranial bone configuration (21.6%). Dysmorphisms of the eye, ear, or nose were detected more frequently in autopsy cases. For trisomy 21, ultrasound showed an aberrant shape of the skull in 14.2% of fetuses. In general, the ocular-orbital and nasal abnormalities in fetuses with trisomy 18 or 21 were more evident in pathological examination than in prenatal ultrasound imaging.

CONCLUSIONS

Facial anomalies are common in the major trisomies, and their prenatal sonographic identification should be improved. The above-mentioned facial anomalies provide sufficient reason to consider performing cytogenic evaluation.

Prenatal diagnosis of craniomaxillofacial malformations: a characterization of phenotypes in trisomies 13, 18, and 21 by ultrasound and pathology

OBJECTIVE

To determine the relationship between trisomies 13, 18, and 21 and craniofacial malformations detected by prenatal sonography.

DESIGN

During a 29-year period (1976 through 2004), prenatal sonographic findings of 69 fetuses with trisomy 13; 171 fetuses with trisomy 18; 302 fetuses with trisomy 21; and 17 fetuses with other trisomies were evaluated retrospectively, after fetal karyotype identification. Sonographic findings were compared with autopsy results in 209 patients (trisomy 13, n=39; trisomy 18, n=64; and trisomy 21, n=106).

RESULTS

For trisomy 13, cleft deformities were detected prenatally in 65.2%, and of the 39 cases with pathological information, 76.9% were found to have a cleft deformity. Ocular and orbital abnormalities were found in 28%. Malformations of the jaws and abnormal profiles were more frequently diagnosed postnatally than prenatally. For trisomy 18, abnormal profiles (41.5%) and ear abnormalities (5.3%) were the most noticeable ultrasound markers, next to abnormalities of the neurocranium (36.8%) and cranial bone configuration (21.6%). Dysmorphisms of the eye, ear, or nose were detected more frequently in autopsy cases. For trisomy 21, ultrasound showed an aberrant shape of the skull in 14.2% of fetuses. In general, the ocular-orbital and nasal abnormalities in fetuses with trisomy 18 or 21 were more evident in pathological examination than in prenatal ultrasound imaging.

CONCLUSIONS

Facial anomalies are common in the major trisomies, and their prenatal sonographic identification should be improved. The above-mentioned facial anomalies provide sufficient reason to consider performing cytogenic evaluation.

Sonographic markers for early diagnosis of fetal malformations

Fetal malformations are very frequent in industrialized countries. Although advanced maternal age may affect pregnancy outcome adversely, 80%-90% of fetal malformations occur in the absence of a specific risk factor for parents. The only effective approach for prenatal screening is currently represented by an ultrasound scan. However, ultrasound methods present two important limitations: the substantial absence of quantitative parameters and the dependence on the sonographer experience. In recent years, together with the improvement in transducer technology, quantitative and objective sonographic markers highly predictive of fetal malformations have been developed. These markers can be detected at early gestation (11-14 wk) and generally are not pathological in themselves but have an increased incidence in abnormal fetuses. Thus, prenatal ultrasonography during the second trimester of gestation provides a “genetic sonogram”, including, for instance, nuchal translucency, short humeral length, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst, that is used to identify morphological features of fetal Down’s syndrome with a potential sensitivity of more than 90%. Other specific and sensitive markers can be seen in the case of cardiac defects and skeletal anomalies. In the future, sonographic markers could limit even more the use of invasive and dangerous techniques of prenatal diagnosis (amniocentesis, etc.).

Non-Invasive Screening Tools for Down's Syndrome: A Review

Down's syndrome (DS) is the most common genetic cause of developmental delay with an incidence of 1 in 800 live births, and is the predominant reason why women choose to undergo invasive prenatal diagnosis. However, as invasive tests are associated with around a 1% risk of miscarriage new non-invasive tests have been long sought after. Recently, the most promising approach for non-invasive prenatal diagnosis (NIPD) has been provided by the introduction of next generation sequencing (NGS) technologies. The clinical application of NIPD for DS detection is not yet applicable, as large scale validation studies in low-risk pregnancies need to be completed. Currently, prenatal screening is still the first line test for the detection of fetal aneuploidy. Screening cannot diagnose DS, but developing a more advanced screening program can help to improve detection rates, and therefore reduce the number of women offered invasive tests. This article describes how the prenatal screening program has developed since the introduction of maternal age as the original "screening" test, and subsequently discusses recent advances in detecting new screening markers with reference to both proteomic and bioinformatic techniques.

The trisomy 18 syndrome

The trisomy 18 syndrome, also known as Edwards syndrome, is a common chromosomal disorder due to the presence of an extra chromosome 18, either full, mosaic trisomy, or partial trisomy 18q. The condition is the second most common autosomal trisomy syndrome after trisomy 21. The live born prevalence is estimated as 1/6,000-1/8,000, but the overall prevalence is higher (1/2500-1/2600) due to the high frequency of fetal loss and pregnancy termination after prenatal diagnosis. The prevalence of trisomy 18 rises with the increasing maternal age. The recurrence risk for a family with a child with full trisomy 18 is about 1%. Currently most cases of trisomy 18 are prenatally diagnosed, based on screening by maternal age, maternal serum marker screening, or detection of sonographic abnormalities (e.g., increased nuchal translucency thickness, growth retardation, choroid plexus cyst, overlapping of fingers, and congenital heart defects ). The recognizable syndrome pattern consists of major and minor anomalies, prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability. Typical minor anomalies include characteristic craniofacial features, clenched fist with overriding fingers, small fingernails, underdeveloped thumbs, and short sternum. The presence of major malformations is common, and the most frequent are heart and kidney anomalies. Feeding problems occur consistently and may require enteral nutrition. Despite the well known infant mortality, approximately 50% of babies with trisomy 18 live longer than 1 week and about 5-10% of children beyond the first year. The major causes of death include central apnea, cardiac failure due to cardiac malformations, respiratory insufficiency due to hypoventilation, aspiration, or upper airway obstruction and, likely, the combination of these and other factors (including decisions regarding aggressive care). Upper airway obstruction is likely more common than previously realized and should be investigated when full care is opted by the family and medical team. The complexity and the severity of the clinical presentation at birth and the high neonatal and infant mortality make the perinatal and neonatal management of babies with trisomy 18 particularly challenging, controversial, and unique among multiple congenital anomaly syndromes. Health supervision should be diligent, especially in the first 12 months of life, and can require multiple pediatric and specialist evaluations.

Ultrasonographic findings of fetal aneuploidies in the second trimester--our experiences

OBJECTIVES

The aim of this study was to determine the incidence of ultrasound findings in common fetal chromosomal defects on a relatively large series coming out from one institution. We also tried to evaluate possible clusters of ultrasound signs of major chromosomal defects.

METHODS

Of the 22,150 fetal karyotypings, 514 abnormal karyotypes (2.3%) were diagnosed prenatally between 1990 and 2004. Of them, 374 were further evaluated for abnormal ultrasound signs in this study. These represented the major chromosomal defects of Down syndrome (n = 207), trisomy 18 (n = 70), trisomy 13 (n = 28) and Turner syndrome (n = 69).

RESULTS

The incidences of major structural defects and minor anomalies were evaluated then sonographic signs with the highest incidences were established in each of the major chromosomal defects. In fetuses with trisomy 13, besides cardiac defects, the most frequently seen structural abnormalities were central nervous system anomalies and facial anomalies. In fetuses with trisomy 18 and trisomy 21, cardiac anomalies were the most common structural sonographic features, whereas the most common findings were hygroma colli and fetal hydrops in fetuses with Turner syndrome. As far as minor anomalies are concerned, increased nuchal fold was the most predictive marker of each major aneuploidy. Choroid plexus cysts were more common in trisomy 18, whereas echogenic intracardiac foci were more frequently detected in fetuses with trisomy 13 and trisomy 21.

CONCLUSION

This study may help to select the most predictive components of the genetic sonogram which may assist the counseling of women for the actual risk of the major chromosomal abnormalities.

Correlation of prenatal sonographic diagnosis and morphologic findings of fetal autopsy in fetuses with trisomy 21

OBJECTIVE

The purpose of this study was to compare the prenatal sonographic and postmortem pathologic findings of fetuses with trisomy 21.

METHODS

Among 22,150 fetal chromosome analyses, trisomy 21 was diagnosed in 207 fetuses between 1990 and 2004. Findings of second-trimester sonography and fetal autopsy were compared by organ system, and their correlation was assigned to 1 of 3 categories.

RESULTS

In total, 83.1% of the 184 fetuses that constituted the final study group had 1 or more abnormal structural findings at postabortion pathologic examination, whereas in 16.9% of the cases, fetal pathologic examination did not reveal any defects in fetal anatomy. Among major structural defects, the agreement between sonographic and autopsy findings was greater than 60% of all abnormalities of these systems: central nervous system (65.4%), heart (67.4%), fetal hydrops (100%), and cystic hygroma (93.3%), whereas the concordance rate was lower in these organ systems: abdominal abnormalities (46.2%), renal anomalies (50%), facial abnormalities (1.2%), and extremities (4.4%). The rate of additional major findings at autopsy was 34.2%. These mainly involved 3 organ systems: heart, head, and abdominal anomalies. Some sonographic findings (n = 16) were not verified at autopsy. The concordances between sonographic and autopsy findings regarding soft markers were considerably high in these markers: increased nuchal fold thickness (72%), short femur/humerus (75%), and pyelectasis (51.9%).

CONCLUSIONS

Examining the correlation between sonography and pathologic findings may indicate possible directions of further development in sonographic screening for trisomy 21. In addition to obstetricians, pediatricians, and geneticists, specialized perinatal pathologists have an important role in the multidisciplinary management of prenatally diagnosed fetal malformations.

Prenatal sonographic findings in 207 fetuses with trisomy 21

OBJECTIVE

The objective was to evaluate the contribution of second trimester ultrasound examination to the prenatal diagnosis of trisomy 21 in 207 fetuses with this aneuploidy. The type and frequency of abnormal sonographic findings were determined. Possible multiple malformation patterns, characteristic of trisomy 21 were sought.

STUDY DESIGN

Singleton fetuses that had prenatal sonography during the second trimester, then underwent cytogenetic evaluation in our institution, made up the study population. The sonographic findings of 207 fetuses with trisomy 21 were analyzed.

RESULTS

Between 1990 and 2004, fetal karyotyping was performed in 22,150 patients for different indications. An abnormal karyotype was diagnosed in 514 cases (2.3%); among them 207 fetuses with trisomy 21 were detected (40.3%). Abnormal sonography was seen in 63.8% of the cases. Structural anomalies were detected in 28.5% of the trisomy 21 fetuses, among them cardiac defects (15.9%), central nervous system anomalies (14.5%), and cystic hygromas (6.8%) were the most common. Of the minor markers, increased nuchal translucency (28%), pyelectasis (20.3%), and shorter extremities (8.7%) were common findings.

CONCLUSIONS

Appropriate diagnosis of structural anomalies, looking for relatively easily detectable minor markers and incorporating fetal echocardiography into the second trimester sonographic protocol, may increase the contribution of mid-trimester ultrasound examination to diagnosing trisomy 21.

The association of echogenic fetal lungs with trisomy 21

OBJECTIVE

To evaluate the association between echogenic appearing lungs on ultrasonographic examination of the fetus and aneuploidy.

METHODS

Cases in which echogenic lungs were prospectively identified on ultrasonographic examination were collected. Other abnormal ultrasonographic findings were documented, as were patient data pertinent to the risk of aneuploidy, such as maternal age and results of serum screening. The chromosomal complement of each identified case is reported.

RESULTS

Five fetuses were identified with diffusely echogenic lungs on ultrasound examination over a two-year period. In three of the five cases, there were other ultrasound abnormalities, although in only one of these was a major congenital abnormality detected. In all three of these cases, the fetal chromosomal complement showed trisomy 21. In 1 of the 2 cases in which the echogenic lungs were an isolated finding, the fetus also was found to have trisomy 21.

CONCLUSIONS

Bilateral and diffusely echogenic lungs appear to have an association with fetal trisomy 21.

Prenatal diagnosis of trisomy 18: report of 30 cases

OBJECTIVES

To review the detection rate of the prenatal screening tests used for the diagnosis of the trisomy 18.

METHODS

From 1 October 1998 to 31 December 2001, we reviewed the database and medical records of 30 cases of trisomy 18. All were singletons and trisomy 18 was confirmed by amniocentesis in 19 cases, by cordocentesis in 6 cases, by chorionic villi sampling in 2 cases and by skin biopsy in 3 cases.

RESULTS

Of the 30 study cases, 23 cases (77%) were offered genetic study due to abnormal ultrasound (US) findings. Twelve (40%) out of the 23 cases were due to abnormal US findings detected before the triple test and 11 (37%) were due to abnormal US findings after the normal triple test. Six cases (20%) were offered genetic study because of an abnormal triple test, and one case was offered genetic study due to advanced maternal age only. Including the second targeted ultrasonogram, one or more abnormal US findings were found in all 30 fetuses.

CONCLUSIONS

Abnormal US finding is the most sensitive screening test for trisomy 18. The most sensitive ultrasonographic finding for trisomy 18 at under 16 weeks of gestation is increased nuchal translucency (75%) and, after 16 weeks, is cardiac defect (83%).

Umbilical cord pseudocyst in a fetus with trisomy 18

An umbilical cord pseudocyst was detected in the 28th week of gestation in a fetus complicated with growth restriction and polyhydramnios. The combination of cord pseudocysts, growth restriction, and polyhydramnios prompted us to perform a detailed ultrasonographic examination (gray scale and three-dimensional), which revealed the presence of micrognathia, overlapping fingers, and congenital heart defects, features characteristic of trisomy 18. Karyotyping confirmed a diagnosis of trisomy 18. After spontaneous labor onset, the infant was delivered at 31 weeks of gestation, and died soon after delivery. An umbilical cord pseudocyst is a good marker for the prenatal detection of trisomy 18.

Sonographic markers of fetal aneuploidy

A variety of ultrasound findings can be identified in fetuses with fetal aneuploidy. Typical findings vary with both the chromosome abnormality and gestational age at time of the ultrasound examination. Increased NT is the primary marker during the first trimester, whereas a variety of markers may be seen during the second trimester. The presence of ultrasound markers increases the risk for fetal aneuploidy, whereas a normal ultrasound reduces the risk. Optimal risk assessment includes consideration of other risk factors including maternal age, family history, and biochemical markers. It is expected that combined risks, incorporating ultrasound findings and biochemistry, will be available in the near future. How first-trimester screening is integrated with second-trimester screening remains to be determined.

Second trimester markers of aneuploidy

The risks of aneuploidy associated with identification of a sonographic marker in the low risk population is controversial. Prior risk estimates have been derived usually from high risk populations. Screening programmes in the first trimester, second trimester and combined first and second trimester will undoubtedly alter the second trimester scan as a screening tool for aneuploidy. This chapter reviews the current sonographic markers and the difficulties in their application to the general population.

Detection of trisomy 18 on formalin-fixed and paraffin-embedded material by fluorescence in situ hybridization

Formalin-fixed and paraffin-embedded autopsy material from 10 fetuses and infants with unknown karyotype and anomalies suggestive of trisomy 18 were subjected to fluorescence in situ hybridization (FISH). Nuclei were extracted from the tissues and hybridized with a chromosome 18-specific centromere probe. The hybridization was successful in 9 of 10 cases. Two cases showed three hybridization signals in most of the nuclei (74% and 85%). These had anomalies frequently occurring with trisomy 18 (congenital heart defect, omphalocele, and horseshoe kidney). Two cases showed a mixture of two and three signals (47%/49% and 59%/36%), suggesting the possibility of mosaicism. One of these cases had anomalies consistent with a trisomy 18 phenotype. In the other case intrauterine growth retardation and syndactylies suggested triploidy. Hybridization with a chromosome 8-specific probe gave a distribution of two and three signals (34% and 62%, respectively). This result strengthened the suspicion of a possible triploid mosaicism. In five of the cases most of the nuclei showed two signals (85% to 88%). However, as only one type of tissue was examined for enumeration of chromosome 18, the possibility of organ mosaicism or other chromosome aberrations cannot be excluded. The FISH technique is applicable on macerated and autolysed formalin-fixed tissue, making it possible to retrospectively analyze autopsy material from aborted and stillborn fetuses and infants. This analysis contributes to a better quality of perinatal autopsies and is helpful in parental counseling.

Early transvaginal measurement of cephalic index for the detection of down syndrome fetuses

OBJECTIVE

The aim of this study was to produce normal cephalic index values by transvaginal scan early in pregnancy and to evaluate the screening utility of this measurement for the identification of fetuses at risk for Down syndrome.

METHOD

In this prospective cross-sectional study, transvaginal high-resolution sonography was performed between 9 and 16 weeks of gestation in 1,087 euploid fetuses and 36 Down syndrome fetuses. Measurements of the cephalic index, calculated as the ratio biparietal diameter/occipito-frontal diameter, were plotted against gestational age.

RESULTS

The cephalic index was found to show fairly constant values throughout the period evaluated. The best correlation with gestational age was described by a linear correlation. All the measurements obtained in Down syndrome fetuses were within the normal ranges.

CONCLUSION

Our data show that in early pregnancy the cephalic index cannot be considered a useful tool in the detection of fetuses at risk for Down syndrome.

Antenatal screening for aneuploidy

There are several methods of antenatal screening for aneuploidy. Most are aimed at the identification of women at increased risk of Down syndrome, the most common abnormal karyotype conferring a significant risk of serious long-term morbidity. Traditional maternal-age-based screening has largely been replaced by programmes based on biochemical markers in maternal serum in the second trimester of pregnancy. However, in recent years there has been a considerable drive towards earlier screening such that there are now a range of potential programmes based on various combinations of maternal age, serum markers and ultrasound findings. There is currently much debate as to which are the most effective methods of screening for aneuploidy.