Sonographic detection of fetuses with trisomies 13 and 18: accuracy and limitations

Sensitivity of prenatal ultrasound for detection of trisomy 18

Objectives: To evaluate the sensitivity of prenatal ultrasound (US) for trisomy (T18) diagnosis and describe US findings in a large tertiary care institution in the USA. Materials and methods: This was a retrospective cohort of all T18 cases diagnosed at our institution from October 2004 to October 2014 based on prenatal or postnatal genetic diagnostic testing. We included all women with a fetus affected by T18 who had a comprehensive US by a maternal-fetal medicine specialist performed at our institution. US findings were reviewed, classified by organ system, and categorized as an anomaly or soft marker. Chi-square or t-test was used for statistical analysis. Results: We included 128 cases of T18 with confirmed cytogenetic analysis -110 (86%) of which were diagnosed prenatally or suspected by cell-free DNA and confirmed postnatally, and 18 of which underwent neonatal blood sampling alone. One hundred and twenty-one (95%) had at least one abnormal US finding. Anomalies were more frequently identified on US at ≥20 weeks as compared with <20 weeks (93% versus 76%; p = .004). The mean number of findings detected per fetus was 5.1 ± 3.0. Fetuses diagnosed by postnatal sampling alone had a similar number of US exams performed and number of abnormal findings compared to those diagnosed prenatally. Conclusion: Ninety-five percent of fetuses with T18 had at least one abnormal US finding. This sensitivity of is higher than reported in most prior studies, but is not 100%, and should be considered when counseling women regarding prenatal diagnosis of T18. Rationale: Historical detection rates for abnormal sonographic findings in trisomy 18 fetuses range from 70% to 100%. These studies are limited by small sample sizes. This is a contemporary study of ultrasound findings in a large group of women with confirmed trisomy 18 by prenatal or postnatal genetic diagnosis. We provide expansive detail on soft markers and anomalies broken down by organ-system and gestational age.

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.

Congenital anomalies of upper extremities: prenatal ultrasound diagnosis, significance, and outcome

OBJECTIVE

We sought to assess the role of ultrasound in the prenatal characterization of fetal malformations of the upper extremities (MUE).

STUDY DESIGN

Ultrasound findings, associated anomalies, pregnancy, and fetoneonatal outcome were analyzed in 100 fetuses with MUE, categorized after Swanson classification of hand congenital abnormalities. Follow-up information was available in all.

RESULTS

Twelve cases had an isolated defect, while 88 showed associated abnormalities involving other organ systems. Fetuses with multiple malformations showed a 76% syndromic risk (32% chromosomal, 41% nonchromosomal), with unfavorable outcome in almost all cases (only 4 survivors, 2 with neurodevelopmental delay). In 27% of syndromic fetuses, the sonographic evidence of the MUE represented the key finding leading to the final diagnosis. The prognosis was usually favorable in cases of isolated defects.

CONCLUSION

A thorough prenatal ultrasound characterization of fetal MUE can assist in the differential diagnosis of many syndromic conditions. When isolated, MUE tend to have a good outcome.

Second trimester prenatal ultrasound for the detection of pregnancies at increased risk of Trisomy 18 based on serum screening

OBJECTIVE

To describe ultrasound findings in fetuses with Trisomy 18.

METHODS

Prospective population-based cohort study of second trimester ultrasound among Californian women who were at increased risk of chromosome abnormality based on serum screening between November 1999 and April 2001. Structural anomalies plus the following soft markers were assessed: nuchal fold thickening, choroid plexus cyst (CPC), echogenic intracardiac focus, echogenic bowel, renal pyelectasis, clenched hands; clinodactyly; short femur, short humerus and a single umbilical artery (SUA).

RESULTS

Overall, 8763 women underwent ultrasound evaluation, including 56 whose fetuses had Trisomy 18. Ultrasound anomalies were seen in 89% of Trisomy 18 fetuses, as compared with 14% of normal fetuses. If the genetic sonogram was normal (no structural anomaly and no soft marker), the risk was reduced by approximately 90%. The ultrasound soft markers were typically seen in conjunction with structural anomalies in affected fetuses and in the absence of a structural anomaly, most isolated ultrasound soft markers were not associated with Trisomy 18. The only exception was an isolated CPC, seen as the only finding in 11% of fetuses with Trisomy 18.

CONCLUSIONS

If the genetic sonogram is used as a sequential test following serum biochemistry, a normal ultrasound study reduces the likelihood of Trisomy 18 substantially even if a woman has abnormal serum biochemistry. The presence of an isolated CPC raises the risk, but not high enough to prompt invasive testing.

Sonographic findings of trisomy 18 in the second trimester of pregnancy

OBJECTIVE

The purpose of this study was to examine the sonographic findings in fetuses with trisomy 18 in the second trimester of pregnancy.

METHODS

A retrospective review of the cytogenetic laboratory databases at 6 tertiary referral centers identified all cases of trisomy 18. The prenatal sonographic studies in fetuses at 15 to 21 weeks' gestation, done before invasive testing for the karyotype, were reviewed for anatomic and biometric findings. We defined abnormal fetal biometric findings as a biometric measurement (biparietal diameter, abdominal circumference, or femur length) below the fifth percentile in the second trimester.

RESULTS

Of 98 fetuses with trisomy 18, 95 (97%) were detected sonographically; an anomaly was found in 92 (94%). A biometric measurement below the fifth percentile was noted in 50 (51%). Cardiac (63%) and central nervous system (34%) anomalies were most frequently detected. Although choroid plexus cysts were commonly seen, no fetuses with trisomy 18 and isolated choroid plexus cysts were found.

CONCLUSIONS

Targeted sonography identified abnormal fetal anatomy or abnormal biometric findings in 97% of fetuses with trisomy 18 in the second trimester. A biometric measurement below the fifth percentile was noted in half of the cases in the second trimester.

Three- and 4-dimensional ultrasonography in the prenatal evaluation of fetal anomalies associated with trisomy 18

OBJECTIVE

The purpose of this study was to assess the usefulness of 3- and 4-dimensional ultrasonography (3D/4DUS) for the description of anomalies associated with trisomy 18 and to determine whether 3D/4DUS adds diagnostic information over what is provided by conventional 2-dimensional ultrasonography (2DUS) alone.

METHODS

Twenty-six fetuses subsequently proven to have trisomy 18 underwent prenatal ultrasonographic evaluations by both 2DUS and 3D/4DUS. Volume data sets were acquired by the same sonographers after the conventional 2DUS examinations and were explored with 4-dimensional imaging software by another independent examiner blinded to the indications of 2DUS. The findings detected by 2DUS and 3D/4DUS were compared with those acquired at autopsy. The sensitivity of each modality for detecting anomalies was calculated and compared by the McNemar test.

RESULTS

Excluding polyhydramnios, there were 131 anomalies confirmed postnatally in 26 fetuses with trisomy 18. There was a statistically significant difference in the sensitivity for detecting anomalies between 3D/4DUS and 2DUS (93.89% versus 73.28%; McNemar value = 23.31; P < .05), especially in anomalies of the face/neck (96.15% versus 65.38%; McNemar value = 6.13; P < .05) and extremities (96.3% versus 48.15%; McNemar value = 11.07; P < .05). Three- and 4-dimensional ultrasonography provided additional diagnostic information for 83.97% of the anomalies related to trisomy 18 and influenced the obstetric management of 4 fetuses.

CONCLUSIONS

Three- and 4-dimensional ultrasonography offered diagnostic advantages for many anomalies associated with trisomy 18, especially for anomalies of the extremities and face. This modality could be a powerful adjunct to 2DUS in the prenatal anatomic evaluation of fetuses with trisomy 18.

Sonographic detection of trisomy 13 in the first and second trimesters of pregnancy

OBJECTIVE

The purpose of this study was to examine sonographic findings in fetuses with trisomy 13.

METHODS

A retrospective review of the cytogenetic laboratory databases at 6 tertiary referral centers identified all cases of trisomy 13. The prenatal sonographic studies in fetuses of less than 22 weeks' gestation, done before invasive testing for karyotype, were reviewed for anatomic and biometric findings. We defined abnormal fetal biometric findings as a biometric measurement (biparietal diameter, abdominal circumference, or femur length) below the fifth percentile in the second trimester.

RESULTS

There were 8 cases of trisomy 13 found in the first trimester and 54 cases found in the second trimester, a total of 62 in all. In the first trimester, 6 of 8 had an anomaly identified (4 with cystic hygroma). In the second trimester, 49 of 54 were identified by sonography; 45 had an anomaly, and 4 had an abnormal fetal biometric measurement without an anomaly. The 5 missed diagnoses had early gestational age (<17 weeks; n = 3) or an inadequate survey secondary to poor visualization. Overall, 22 of 54 fetuses with trisomy 13 had an abnormal biometric measurement. The most common anomalies detected in the second trimester were heart defects (n = 34), central nervous system anomalies (n = 30), facial clefts (n = 19), abnormal hands (n = 13), and genitourinary anomalies (n = 9).

CONCLUSIONS

Targeted sonography identified abnormal fetal anatomy or abnormal biometric measurements in 95% of fetuses with trisomy 13 in the second trimester after 17 weeks' gestation. A biometric measurement below the fifth percentile was noted in nearly half of cases in the second trimester.

The second trimester genetic sonogram

The genetic sonogram, a fetal anatomic survey targeted at identifying features associated with aneuploidy, is carried out between 15 and 20 weeks' gestation. It has evolved as an adjunctive screening tool capable of further refining the individualized risk-calculation for trisomy that is based on maternal age or serum screening markers. The significance of a range of major structural anomalies and so-called "soft-markers" for trisomy, detected both in isolation and in combination, has been widely investigated. This review serves to describe the key components of the second trimester genetic sonogram and to illustrate how these markers are integrated into risk assessment for aneuploidy.

Genetic basis for congenital heart defects: current knowledge: a scientific statement from the American Heart Association Congenital Cardiac Defects Committee, Council on Cardiovascular Disease in the Young: endorsed by the American Academy of Pediatrics

The intent of this review is to provide the clinician with a summary of what is currently known about the contribution of genetics to the origin of congenital heart disease. Techniques are discussed to evaluate children with heart disease for genetic alterations. Many of these techniques are now available on a clinical basis. Information on the genetic and clinical evaluation of children with cardiac disease is presented, and several tables have been constructed to aid the clinician in the assessment of children with different types of heart disease. Genetic algorithms for cardiac defects have been constructed and are available in an appendix. It is anticipated that this summary will update a wide range of medical personnel, including pediatric cardiologists and pediatricians, adult cardiologists, internists, obstetricians, nurses, and thoracic surgeons, about the genetic aspects of congenital heart disease and will encourage an interdisciplinary approach to the child and adult with congenital heart disease.

Trisomy 18: Fetal ultrasound findings at different gestational ages

The aim of this article is evaluate the sonograhic findings in fetuses with trisomy 18 at different gestational ages. The cases were recruited from pregnant women, who underwent to prenatal diagnosis in the period from October 1995 to September 2006. Seventy-one fetuses with trisomy 18 were diagnosed. On review of the sonograms the majority of these cases had ultrasound anomalies (sensitivity of 91.5%). The most frequent anomalies were abnormalities of extremities (40.8%) and fetal growth restriction (35.2%). More frequently (54.9%) two or more anomalies were present. Nearly all fetuses with trisomy 18 had sonographic abnormalities. Likely improved high-resolution equipment and attention to details by skilled operators led to the detection of most anomalies to trisomy 18. Knowledge of types of specific ultrasound findings can improve prenatal diagnosis in order to provide invasive procedures only when indicated, and to avoid amniocentesis when ultrasound signs are not observed in women at high risk from positive biochemical testing.

Role of second trimester sonography in detecting trisomy 18: a review of 70 cases

PURPOSE

To investigate the role of second-trimester sonographic examination in the prenatal diagnosis of trisomy 18.

METHODS

Out of 22,150 fetal chromosomal analyses performed between 1990 and 2004, 70 trisomy 18 fetuses were found. The sonographic findings of this aneuploidy were analyzed.

RESULTS

The average maternal age was 32.4 years; the average gestational age was 19.5 weeks. Major anomalies were seen in 61 (87.1%) of the 70 fetuses with trisomy 18; among these, cardiac anomalies were the most common (47.1%), with a 27.1% incidence of ventricular septal defects. Anomalies of the central nervous system were seen in 35.7% of cases; abnormal head shape was the most frequently detected anomaly in this group (12.9%). Fifty-six (80%) of the fetuses had at least 1 minor anomaly; of these, choroid plexus cyst was the most common (38.6%). Increased nuchal fold thickness was detected in 17.1% of cases.

CONCLUSION

The vast majority of trisomy 18 fetuses have sonographically detectable abnormalities in the second trimester. Both the 87.1% frequency of major anomalies and the 80% frequency of minor anomalies are substantially higher than multiple biochemical marker tests could achieve. It was also demonstrated that fetal echocardiography plays a pivotal role in the diagnosis of trisomy 18.

Trisomy of chromosome 18 in the baboon (Papio hamadryas anubis)

Trisomy 18 is usually a lethal chromosomal abnormality and is the second most common autosomal trisomy in humans, with an incidence of 1:8000 live births. It is commonly associated with abnormalities of the lower and upper extremities, having the frequency of 95% and 65%, respectively. A newborn female olive baboon (Papio hamadryas anubis) was diagnosed with intrauterine growth retardation and severe arthrogryposis-like congenital joint deformities. Cytogenetic analysis including G-banding and fluorescence in situ hybridization (FISH) revealed that the congenital abnormalities were associated with chromosomal mosaicism for trisomy 18. Genetic analysis with microsatellites from chromosome 18 confirmed the maternal origin of the extra chromosome 18. This is the first report of trisomy 18 in the baboon, which may be a promising animal model of human disease.

Congenital curly toe of the fetus

OBJECTIVES

To assess the prevalence, prenatal detection rate, and associated anomalies of congenital curly toe in an unselected obstetric population.

METHODS

Between September 2001 and July 2002, 1167 singleton fetuses in the second and third trimesters underwent routine prenatal ultrasound at our hospital. Congenital curly toe was diagnosed when the fourth or fifth toe was not fully delineated on the axial image with medial and plantar flexion on the coronal image. All neonates underwent a physical examination within 3 days after delivery. Radiography was performed on those infants with curly toe. We assessed the prevalence, prenatal detection rate, and associated anomalies of the condition.

RESULTS

There were 38 congenital curly toes among the 1167 neonates, yielding a total prevalence of 32.6 per 1000. In 26 of the 38 the fourth toe was curly and in 12 the fifth toe was curly. Of those in which the fourth toe was curly, 26.9% involved the right toe, 65.4% the left, and 7.7% involved both toes. For a curly fifth toe, these values were 25.0%, 16.7% and 58.3%, respectively. There was no associated structural anomaly, chromosomal abnormality, or syndrome in any case. Sixteen of the 38 curly toes were detected on prenatal ultrasound, including 13 of 26 with the fourth toe being curly and three of 12 with the fifth being curly.

CONCLUSIONS

Congenital curly toe is not an uncommon condition, and can be detected on the prenatal ultrasound. Although it usually appears as an isolated finding without clinical significance, thorough ultrasound examination of the fetus should be recommended.

Congenital diaphragmatic hernia: is 15q26.1-26.2 a candidate locus?

Congenital diaphragmatic hernia is a developmental abnormality due to failure of the normal formation of the diaphragm. While the majority of cases are idiopathic, chromosomal abnormalities have been implicated in approximately 15% of cases. Several recent series have suggested that 15q24-26 is critical in normal development of the diaphragm. We present a patient with a karyotype of 46, XX, del (15)(q26.1) born with a diaphragmatic hernia, coarctation of the aorta, and dysmorphic features. This patient represents the smallest isolated chromosomal aberration on distal 15q reported to date. The DNA regulatory proteins, myocyte-specific enhancer factor 2 proteins (MEF2), play a critical role in the control of muscle differentiation and development. One member of this gene family, MEF2A, maps to 15q26. We propose that this region is a candidate locus for diaphragmatic hernia and future investigations should examine the role of MEF2A in diaphragm formation.

Screening for aneuploidy: the genetic sonogram

Over the past 10 years, the use of ultrasound in aneuploidy risk estimation has improved the way obstetrics is practiced. It allows patients to obtain more personalized risk assessment and has allowed many women a reasonable alternative to invasive testing. The addition of soft markers to the sonographic screening for aneuploidy has been extremely beneficial, especially when considered in combination with other ultrasound findings. The best estimate of risk seems to be achieved through the combined use of ultrasound, maternal serum screening, and maternal age. The literature supports the use of soft markers only when applied to the high-risk population, where the prevalence of aneuploidy is increased. If this information is applied to the low-risk populations, especially in isolation, the lower prevalence of aneuploidy makes the positive predictive value too low to be of any value in counseling patients. As with many screening tests it occasionally misses the diagnosis, and every patient needs to understand this potential shortcoming. It is a personal decision regarding their willingness to accept the risk of a missed diagnosis versus the risk of fetal loss from an invasive procedure. Although it is far from perfect, in the right hands and with appropriate counseling ultrasound is an excellent tool. This is such an important decision for women and their families, and it is worth the time it takes to explain the benefits and limitations of this test.

Second-trimester sonography and trisomy 18

OBJECTIVE

This report presents the findings seen on initial second-trimester sonography in a large group of fetuses with trisomy 18. The object of this study was to describe the types and frequencies of abnormal sonographic findings seen and to further evaluate those cases in which no abnormal findings were noted.

METHODS

A retrospective chart review of the prenatal sonograms in cases of trisomy 18 was conducted.

RESULTS

Forty-nine fetuses with trisomy 18 were examined by second-trimester sonography. Multiple fetal anomalies were seen in most cases. The most frequent structural findings involved the brain (82%), heart (55%), and upper extremities (53%). Growth abnormalities occurred in 39% of these fetuses. Choroid plexus cysts were the most common individual findings. Larger cysts increased the likelihood of trisomy 18, although no fetuses with trisomy 18 had isolated choroid plexus cysts. Seven fetuses (14%) had no anomalies seen on their initial scans. In each of these scans, the fetal anatomy was incompletely visualized because of technical constraints. Six had subsequent scans approximately 2 weeks later, which showed abnormal sonographic findings.

CONCLUSIONS

Most fetuses with trisomy 18 were identified by structural anomalies, typically seen in the brain, heart, and upper extremities. Larger choroid plexus cysts were associated with this aneuploidy. Technical factors, which limit fetal visualization, were noted in all cases in which no sonographic abnormalities were detected during the initial sonographic examinations. Detection of abnormal cases will rely on a completed evaluation of a routine fetal anatomic survey.

Prenatal detection of fetal trisomy 18 through abnormal sonographic features

OBJECTIVE

To describe the prenatal detection of fetal trisomy 18 through abnormal sonographic features and to determine the sensitivity of sonographically detecting fetuses with trisomy 18.

METHODS

All genetic and cytogenetic records of fetuses with trisomy 18 were reviewed retrospectively (1992-2002). From these, singleton fetuses who had prenatal sonography at our unit were identified. The maximal numbers of individual abnormalities from 1 sonographic examination (not limited to type of organ system) were recorded. Each abnormality was classified as major, minor, or "other," and each organ system was classified as abnormal only once, regardless of the number of individual abnormalities identified in that system. The sensitivity of sonography in detecting abnormalities of trisomy 18 was determined.

RESULTS

Of 38 fetuses identified with trisomy 18, all had 4 or more prenatally detected sonographic abnormalities (sensitivity of sonographic detection of fetuses with trisomy 18, 100%). The median number of abnormalities per examination was 8 (range, 4-19). Sonographically detected major abnormalities were cardiac (84%; n = 32), central nervous system (87%; n = 33), gastrointestinal (26%; n = 10), and genitourinary (16%; n = 6). Sonographically detected minor abnormalities were short ear length below the 10th percentile for gestational age (96%; n = 26/27), upper extremities and hands (95%; n = 36), lower extremities and feet (63%; n = 24), and face (53%; n = 20). Fifty percent (19 of 38) had choroid plexus cysts identified, but this was never an isolated finding.

CONCLUSIONS

In experienced hands, the sensitivity of detecting fetal trisomy 18 on prenatal sonography is 100%, and all cases will have multiple anomalies visualized.

Sonographic features of trisomy 18 at midpregnancy

OBJECTIVE

To evaluate the sonographic characteristics of the fetuses with trisomy 18 at 16-22 weeks of gestation.

METHODS

The subjects were recruited from pregnant women undergoing prenatal sonographic examinations at 16-22 weeks of gestation and subsequently proven to be trisomy 18. The results of ultrasound findings were retrospectively reviewed in 25 cases with chromosomes which were confirmed as trisomy 18.

RESULTS

All cases had at least one abnormal sonographic finding. There was only one case that had no structural abnormality, but fetal growth restriction was documented. The common sonographic findings included fetal growth restriction, choroid plexus cysts, cardiac anomalies, clenched hand, omphalocele and cleft lip. Fetal growth restriction was the most common finding demonstrated in nearly half of all cases. Other less common findings were diaphragmatic hernia, abnormal head shape, polyhydramnios, single umbilical artery.

CONCLUSION

Nearly all fetuses with trisomy 18 had characteristic sonographic patterns of abnormalities demonstrated at midpregnancy. Detailed ultrasound at midpregnancy could effectively screen fetuses with trisomy 18 for further genetic testing.

Second trimester ultrasound screening for chromosomal abnormalities

The use of prenatal ultrasound has proven efficacious for the prenatal diagnosis of chromosomal abnormalities. The first sonographic sign of Down syndrome, the thickened nuchal fold, was first described in 1985. Since that time, multiple sonographically-identified markers have been described as associated with Down syndrome. The genetic sonogram, involving a detailed search for sonographic signs of aneuploidy, can be used to both identify fetuses at high risk for aneuploidy and, when normal, can be used to decrease the risk for aneuploidy for a pregnancy when no sonographic markers are identified. Combining the genetic sonogram with maternal serum screening may be the best method of assessing aneuploidy risk for women who desire such an assessment in the second trimester. Trisomy 18, Trisomy 13, and triploidy are typically associated with sonographically identified abnormalities and have a high prenatal detection rate. The use of the described sonographic signs in low-risk women requires further investigation, however, patients at increased risk for aneuploidy due to advanced maternal age or abnormal serum screening can benefit from a genetic sonogram screening for sonographic signs of aneuploidy to adjust their baseline risk of an affected fetus.

Four years experience of first-trimester nuchal translucency screening for fetal aneuploidies with increasing regional availability

BACKGROUND

A prospective screening study was carried out at the regional genetic and perinatal center in South Hungary in order to determine the efficiency of first-trimester nuchal translucency screening for fetal aneuploidies, following augmentation of the availability of nuchal translucency screening in the region by the inclusion of newly-trained hospital sonographers.

METHODS

Nuchal translucency thickness was measured by transvaginal sonography in 7,044 women with singleton or multiple pregnancies at weeks 10-12. Fetal karyotyping was performed when the nuchal translucency was . or = 2.5 mm, and in women with fetuses at high cytogenetic risk.

RESULTS

Follow-up was performed in 6,841 of the 7,044 screened women. An abnormal karyotype was found in 33 cases (0.48%). The level of increased nuchal translucency was 4.5% at a cutoff of > or = 2.5 mm, and 2.8% at a cutoff of > or = 3 mm. Seventeen cases of trisomy 21, eight of trisomy 18, four of trisomy 13, one of 45,X, one of triploidy and two cases with other chromosomal abnormalities were detected. In the 33 fetuses with a chromosomal abnormality, the nuchal translucency thickness was <2.5 mm in a case of trisomy 18, > or = 2.5 mm in 32 cases and > or = 3 mm in 28 cases. With cutoffs of 2.5 mm and 3 mm, the sensitivity was 96.97% and 84.85%, respectively.

CONCLUSIONS

Application of a nuchal translucency thickness cutoff of 2.5 mm is highly efficient for the screening of fetal aneuploidies at 10-12 weeks. This efficiency can be maintained by increasing the regional availability of nuchal translucency screening through the inclusion of newly-trained hospital sonographers.

Prenatal diagnosis and management of abnormalities in the urologic system

We have reviewed the prenatal diagnosis and management of abnormalities in the urologic system. Urologic anomalies may be caused by embryologic aberrations, genetic disease, or a nonrandom association with other structural abnormalities. There is a wide range of prognoses, depending on the cause and the impact of the anomaly on the production of amniotic fluid. Management focuses on obtaining an accurate prenatal diagnosis, providing appropriate counseling, and ensuring the proper surveillance or treatment before and after birth.

Isolated polydactyly: prenatal diagnosis and perinatal outcome

Our objective was to determine the clinical significance of isolated polydactyly identified on prenatal sonogram. All patients with sonographically detected isolated polydactyly scanned over an 11-year period were identified from our database. All patients underwent detailed surveys, and follow-up was obtained by review of the medical records and telephone conversations with parents and referring physicians. Thirteen patients with isolated polydactyly were identified. Follow-up was available in 12 patients. Indications for referral included advanced maternal age (2), second-opinion polydactyly (4), family history of polydactyly (1), uncertain dates (5), and growth (1). The gestational ages at the times of sonographic diagnosis ranged from 17.5 to 34 weeks with all but one case being identified before 23 weeks. Prenatal identification included polydactyly of the upper limb (8), lower limb (4), and both upper and lower limbs (1). Postaxial polydactyly was seen in 12 patients and preaxial in one. Polydactyly was confirmed in all 12 cases in which follow-up was available. Karyotypes were normal in all five fetuses in which amniocentesis was performed. Ten of 12 fetuses were born alive, one died in utero at 34 weeks as a complication of severe pre-eclampsia and one died at term as a result of a cord accident. No surviving neonate had any other identifiable malformation or suspected karyotypic abnormality. In conclusion isolated polydactyly identified by prenatal sonography is associated with good perinatal outcome.

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.

The role of reduced ear size in the prenatal detection of chromosomal abnormalities

A prospective ultrasound study was performed between 18 and 38 weeks' gestation on 29 fetuses in a high-risk population, defined by the presence of structural anomalies, in order to investigate the usefulness of fetal ear measurements in the prenatal prediction of chromosomal abnormality. The prevalence of abnormal chromosomes was 34 per cent. The sensitivity (SE), specificity (SC), positive predictive values (PPV), and negative predictive values (NPV) of ear length for the detection of chromosomal abnormality were 80, 84.2, 72.7 and 88.9 per cent. The SE, SC, PPV, and NPV of ear width were 40, 94.7, 80 and 75 per cent. Fetal ear measurements may be a useful adjunct to the various ultrasound parameters in the prenatal detection of chromosome abnormality in a high-risk population of fetuses with structural anomaly(ies).

Establishment and application of a normal range for nuchal translucency across the first trimester

Before chorionic villus sampling at 10-13 weeks' gestation, 453 women had the crown-rump length and nuchal translucency (NT) measured with transabdominal ultrasound. There were 19 aneuploid pregnancies (ten cases of trisomy 21, six of trisomy 18, one of 47 + marker, one 47,XXX, and one 45,X mosaic). Average NT was 1.7 mm (range 0-5 mm), correlating with the crown-rump length, but not maternal age. A static cut-off of 2.5 mm gave a false-positive rate of 1.3 per cent for crown-rump length between 30 and 35 mm, rising to 13 per cent in fetuses with a crown-rump length between 50 and 65 mm. This gave an overall false-positive rate of 5.5 per cent for a detection rate of 30 per cent for trisomy 21. Applying a dynamic action limit (95th centile), the false-positive rate remained at 5 per cent irrespective of the crown-rump length, detecting 30 per cent of trisomy 21 and 36.8 per cent of all aneuploidies. Raising the action limit to the 97.5th centile halved the false-positive rate (2.5 per cent), with no change in trisomy 21 detection and only a slight decrease in aneuploidy detection (31.6 per cent). Aneuploid fetuses showed normal first-trimester growth. NT increases with gestational age, making a dynamic action limit necessary to decrease the false-positive rate, while maintaining aneuploidy detection rates. Aneuploidy does not cause significant first-trimester growth retardation, enabling normal ranges for NT with crown-rump length to apply.

The significance of ultrasonographically diagnosed fetal wrist position anomalies

OBJECTIVE

Our purpose was to determine the clinical significance of ultrasonographically diagnosed fetal wrist position anomalies.

STUDY DESIGN

The relationship of the fetal hand to the forearm was prospectively evaluated in all second- and third-trimester scans over a 5-year period. If an abnormal wrist position was detected, a targeted scan, including echocardiography, was performed. The outcomes of abnormal pregnancies were obtained.

RESULTS

An abnormal relationship of the hand to the forearm was found in 22 fetuses in 27,467 scans. Nine had a normal karyotype, and 13 had an abnormal karyotype. Among the nine with normal chromosomes, three had evidence of a movement disorder. Three with normal karyotypes are alive; two of these are the only normally functioning survivors. They had no other major anomalies and were shown prenatally to have normal movement of the limbs.

CONCLUSIONS

An abnormal fetal wrist position is associated with a high incidence of karyotype and movement abnormalities.

Evaluation of Fetal Hands With Ultrasound During a Routine Obstetric Examination

In this prospective study, 100 second trimester fetuses were assessed to determine the frequency of visualization of the open fetal hands and the three phalanges of the fifth digit during a routine ultrasound examination. Open right hands were seen in 82 (82%) fetuses, and the three phalanges of the right fifth digit were seen in 71 (71%) fetuses. Open left hands were visualized in 80 (80%) fetuses, and the three phalanges of the left fifth digit were seen in 70 (70%) fetuses. Both open hands were seen in 73 (73%) fetuses, and only one open hand was seen in 17 (17%) fetuses. Fetal abnormalities, such as clenched hands with or without overriding fingers, hypoplasia of the middle phalanx of the fifth digit, or clinodactyly of the fifth finger, have been reported to be associated findings of certain fetal chromosomal disorders (e.g., trisomies 13, 18, and 21) and may initiate further genetic evaluation. The present study shows that it is feasible to include the assessment and documentation of fetal hands in the routine obstetric ultrasound examination without significantly increasing the scanning time.

Ultrasound screening for fetal abnormalities

Ultrasound screening for fetal abnormalities is increasingly becoming part of routine antenatal care in Europe and the UK. However, there has been very little formal evaluation of this practice. In this article reports of routine ultrasound screening are reviewed and the advantages and disadvantages discussed. The majority of routine anomaly scanning is done in the second trimester but there may be a case for screening at other times in pregnancy and alternative anomaly screening policies are discussed.

Clinical significance of fetal choroid plexus cysts

Choroid plexus (CP) cysts are commonly detected on routine mid-trimester ultrasound scan. When associated anomalies are detected, the risk is sufficient to justify an invasive diagnostic test such as amniocentesis. However, the risk when no associated anomalies are detected is much less well defined. This information is required to determine the appropriate management in cases of apparently isolated CP cysts. We thought the only way to resolve the difficulties in counselling prospective parents was to conduct a prospective study in a large unselected population. A registry of fetal CP cysts detected over 3 years in the Yorkshire Region was compiled and we identified 524 CP cysts. These cases were then amalgamated and analysed with 1361 cases from prospective studies reported in the world English literature and a further 71 unpublished cases identified from a 2 year prospective series from Ninewells Hospital, Dundee. The risk of chromosomal abnormalities was 1 in 150 (95% CI 1 in 85, 1 in 261) when no fetal anatomic abnormalities, apart from the CP cysts themselves, were detected antenatally. The risk increased to approximately 1 in 3 if any other associated ultrasound abnormalities were detected antenatally. The risk did not appear to be related to whether or not cyst size diminished as gestation progresses, whether they were unilateral or bilateral, and whether they were small or large in size (60-80% < 10 mm). 76% of aneuploidic cases were trisomy 18 and 17% were trisomy 21. The risk of Down's syndrome in fetuses with CP cysts but no other anomalies detected antenatally is 1 in 880. The probability of a chromosomal abnormality is high when CP cysts are associated with any other antenatally detected anomaly, indicating a clear need to offering amniocentesis. The predictive value is much lower when no other anomalies are detected. In such cases, it is probably advisable to regard CP cysts as an indication for detailed ultrasound assessment, rather than invasive testing.

Fetal cholecystomegaly: a prenatal marker of aneuploidy

The fetal gall bladder can now be easily identified during the second and third trimesters using high-resolution ultrasonography. In this report we present eight fetuses with an enlarged gall bladder detected on prenatal ultrasonography at a mean gestational age of 24.6 weeks (range 19-31 weeks). Additional ultrasonographic findings were present in four cases: fetal anomalies and intrauterine growth retardation in three and polyhydramnios in one. Of those cases associated with fetal anomalies, one women underwent amniocentesis at 21 weeks revealing trisomy 18. The other two declined prenatal karyotyping; neonatal karyotyping revealed trisomy 13 in one and trisomy 18 in the other. Although an enlarged fetal gall bladder can be a normal variant in the second and third trimesters, the prenatal detection of cholecystomegaly should prompt a search for associated anomalies and other markers of aneuploidy. If found, prenatal karyotyping should be considered.

First trimester diagnosis of cystic hygromata using transvaginal ultrasound and cytogenetic evaluation

We studied the outcome of fetuses in whom cystic hygroma was diagnosed in the first and early second-trimester of pregnancy using transvaginal ultrasonography. The purpose of this study was to evaluate the association between fetal cystic hygroma and fetal cytogenetic abnormalities, and the long-term prognosis. Thirty-five consecutive fetuses between 9.1 and 13.4 weeks of gestation diagnosed as having a nuchal hygroma were evaluated ultrasonographically and karyotyped. Those with a normal chromosome complement were ultrasonographically monitored throughout the remainder of the pregnancy to document the resolution of the hygroma. Eighteen of thirty-five fetuses were found to have a normal karyotype and five of these were aborted electively. The hygromas resolved in ten of these karyotypically normal fetuses within four weeks of initial diagnosis and they were phenotypically normal at birth. Seventeen fetuses were karyotypically abnormal with trisomy twenty-one being the most common abnormality. Prenatal cytogenetic analysis should be offered to women with fetal cystic hygroma diagnosed in the first trimester. A normal outcome is likely in those without chromosome abnormalities.

Isolated choroid plexus cysts--the need for routine offer of karyotyping

The management of isolated fetal choroid plexus cysts remains controversial. We have prospectively studied 15,565 pregnancies at two large obstetric units for the presence of choroid plexus cysts. In all cases where cysts were present at 19 weeks' gestation or greater, and were multiple, bilateral or solitary and greater than 5 mm maximum diameter, women were offered amniocentesis or placental biopsy, irrespective of the presence or absence of other abnormalities. Choroid plexus cysts were present in 152 (0.98 per cent) of cases. Four cases (2.6 per cent) of autosomal trisomy (three of trisomy 18, one of trisomy 21) were detected on prenatal karyotyping. In all cases, choroid plexus cysts were the only detectable prenatal anomaly. This study and a review of other large studies do not support the view that isolated choroid plexus cysts are a benign variant, the risk of trisomy being 1 in 82. Until further evidence is available, we recommend that cases of isolated fetal choroid plexus cysts at 19 weeks' gestation or greater should be offered prenatal karyotyping.

Prediction of an abnormal karyotype in fetuses with omphalocele

The aim of this study was to assess the value of ultrasonographic evaluation in predicting abnormal karyotypes in fetuses with omphalocele. Forty fetuses with antenatally diagnosed omphalocele and available karyotype results were reviewed. Ultrasound evaluation included herniation contents and size, and the detection of other anomalies. Nine of 40 consecutive fetuses had abnormal karyotypes: trisomy 18 (n = 5), trisomy 13 (n = 3), 47,XXX (n = 1). Only 1/25 with an extracorporeal liver versus 8/15 with an intracorporeal liver had abnormal chromosomes [P = 0.0006, RR = 0.14 (0.02 < RR < 0.9)]. Small defects (< 3 cm) were associated with abnormal karyotypes [P = 0.01, RR = 4.7 (1.4 < RR < 15.6)]. Finding concurrent malformations was highly associated with chromosomal anomalies [P = 0.00004, RR = 4.4 (2.3 < RR < 8.5)]. The presence of associated malformations, an intracorporeal liver, and a small herniation size are highly suggestive of an associated abnormal karyotype.

Natural history of trisomy 18 and trisomy 13: I. Growth, physical assessment, medical histories, survival, and recurrence risk

The natural history of trisomy 18 and trisomy 13 was investigated using data derived from parent questionnaires and medical records from 98 families with an index case of trisomy 18 and 32 families with an index case of trisomy 13. Data are presented on pregnancy, delivery, survival, medical complications, immunizations, growth, cause of death, cytogenetics, and recurrence risk. Half of the trisomy 18 babies were delivered by C-section. Fetal distress was a factor in half, and the only reason in a third of C-section deliveries. One minute Apgar scores were significantly lower in C-section and breech deliveries. There were more small for gestational age babies than in the general population, but most of the low birth weight newborns were small for gestational age, unlike the general population. Survival in this group of children was better than in other studies due to ascertainment bias. There were more girls than boys at all ages for both conditions, and the sex ratio decreased with time. Growth curves for length, weight, head circumference, and weight vs height are provided. Long-term survival did not appear to be due to mosaicism. We found no adverse reactions attributable to immunizations. At age 1 year there was an average of approximately 2 operations per living child. We report the second case of successful major cardiac surgery in a trisomy 18 child. Almost 70% of deaths were attributed to cardiopulmonary arrest. The sibling recurrence risk for trisomy 18 or trisomy 13 was 0.55%.

Techniques in current use in prenatal diagnosis

Prenatal diagnosis is now offered to the majority of pregnant women in Europe and the United States. Advances in obstetric and laboratory techniques mean that increasing numbers of conditions can be diagnosed prenatally; indeed, gene carriers can be identified before pregnancy in some cases. Current obstetric and laboratory techniques for prenatal screening and diagnosis of genetic disorders are discussed.

Characteristics of structural heart defects in trisomy 9 and their relationship to those in trisomy 13, 18, and 21

The hearts from two live-born full-term infants with nonmosaic trisomy 9 (one complete trisomy 9, one partial trisomy 9) were studied after death. Both demonstrated conal and valvular anomalies associated with ventricular septal defects. These specific malformations are discussed in relation to published cases of trisomy 9 and the cardiac defects of other autosomal trisomies (13, 18, and 21).

Prenatal Sonographic Renal Findings Associated with Trisomy 13

Prenatal ultrasonographic renal findings are described in three cases of trisomy 13. The association of renal anomalies, including hyperlobulation, dysplasia and presence of cortical cysts, with trisomy 13 has been reported previously. This series, however, points out the importance of considering trisomy 13 as a possible diagnosis and recommends prenatal diagnosis when renal abnormalities are found on ultrasound examination.

First-trimester diagnosis of cystic hygroma--course and outcome

OBJECTIVE

We studied the outcomes of fetuses in whom cystic hygroma was diagnosed in the first trimester of pregnancy through the application of transvaginal ultrasonography.

STUDY DESIGN

In the period 1990 to 1991 22 fetuses with cystic hygroma were found. All fetuses had karyotyping and a complete ultrasonographic search for associated anomalies.

RESULTS

Aneuploidy was found in seven of 22 fetuses: four trisomy 21, two trisomy 18, and one translocation. Monosomy X was absent in this series. In 15 of 22 cases there was a normal karyotype. In 10 of 15 euploid fetuses the small nonseptated hygroma resolved spontaneously. In four of 15 euploid fetuses other malformations were detected with ultrasonography (i.e., polycystic kidneys, coarctation of the aorta, bladder outlet obstruction, and fetal hydrops).

CONCLUSION

Whenever a cystic hygroma is suspected in the antenatal period, even if of small size, a structured and detailed ultrasonographic examination and fetal karyotyping are recommended.

Screening for Down syndrome with the femur length/biparietal diameter ratio: a new twist of the data

OBJECTIVE

The purpose of this study was to determine the value of discordant morphometric measurements as identifiers of Down syndrome by evaluating the relationship of biparietal diameter, femur length, biparietal diameter/femur length ratio, and cephalic index between a group of fetuses with trisomy 21 and a control population.

STUDY DESIGN

Biometric measurements from 48 fetuses with trisomy were reviewed and compared with 107 normal fetuses of similar gestational age. Data were analyzed in 2-week gestational age intervals to determine the effect of gestational age on ultrasonographic detection of Down syndrome. Outcome measures were subject to least-squares linear regression and the t test for analysis.

RESULTS

A positive relationship between abnormal morphometric measurements and fetuses with Down syndrome was detected but only during specific weeks of pregnancy.

CONCLUSION

Although it appears that biometric measurements may be useful for Down syndrome, further study is needed before its widespread introduction into clinical practice.