Trends in Invasive Prenatal Diagnosis: Effect of Sequential Screening and Noninvasive Prenatal Testing.

OBJECTIVE: To examine trends in the incidence and method of invasive prenatal diagnosis due to the impact of sequential screening and noninvasive prenatal testing. METHODS: This is a retrospective review of all pregnancies that have undergone invasive prenatal diagnostic testing between June 2002 and June 2014, divided in 3 periods: period 1 from June 2002 to October 2006, period 2 from November 2006 to December 2011, and period 3 from January 2012 to June 2014. The main outcome measures were trends in the incidence and method of each procedure. RESULTS: There were 88,135 deliveries and 6,080 invasive procedures during the study period. In period 1, 2,755 (8.8%) procedures were carried out, in period 2 2,820 (7.3%), and in period 3 505 (2.5%; p < 0.01). In period 1, there were 1,990 (6.3%) cases of amniocentesis, 1,646 (4.3%) in period 2, and 254 (1.2%) in period 3 (p < 0.01). In addition, in 765 (2.5%) cases, chorionic villus sampling (CVS) was performed in period 1, compared to 1,174 (3.0%) cases in period 2 and 251 (1.3%) cases in period 3 (p < 0.01). Advanced maternal age as the sole indication for invasive procedures decreased significantly over time, while the indication of abnormal serum screening and abnormal ultrasound findings increased (p < 0.01). CONCLUSION: There was a significant decline in the incidence of invasive prenatal testing over the 12 years of the study. The decrease in amniocentesis was more marked than that in CVS.

The importance of a genetic evaluation of prospective ovum donors: a study of family history and genetic carrier testing.

OBJECTIVE: To determine the percentage of potential ovum donors who have an increased risk for fetal harm. STUDY DESIGN: Couples using an ovum donor to conceive a pregnancy are expecting to select someone who poses a low genetic risk to their offspring. Currently, most genetic carrier screening of these donors is performed at the discretion of the fertility center. This investigation involves a review of family history and genetic carrier test results of oocyte donor candidates. RESULTS: A total of 210 (22.1%) of 950 potential oocyte donors had at least one fetal risk factor based on family history. Of 244 prospective donors who had genetic testing, 15 (6.1%) were found to be carriers of hereditary diseases that could pose an increased risk to a fetus. CONCLUSION: A genetic assessment is a critical step in the evaluation of prospective oocyte donors, because almost one quarter of donors had a family history of a disease that could pose an increased fetal risk. Disclosure of ovum donor carrier status and, when applicable, testing of partners is required before accepting a potential ovum donor in an infertility program.

Complete trisomy 21 vs translocation Down syndrome: a comparison of modes of ascertainment.

OBJECTIVE: To compare the indications for invasive prenatal testing resulting in the detection of translocation Down syndrome and complete trisomy 21. STUDY DESIGN: This case control study was based on a large amniocentesis and chorionic villi samples database (n = 534,795). All specimens with translocation Down syndrome (n = 203) comprised the translocation group and were compared with a maternal age-matched group (4 to 1, n = 812) in which complete trisomy 21 was detected. Women with a normal karyotype were randomly selected (n = 812) and served as controls. Indications for invasive testing were compared among the 3 paired groups using χ(2) analysis. RESULTS: There were no differences in the incidence of abnormal first- and second-trimester screening tests between the translocation Down syndrome and the complete trisomy 21 groups. History of prior aneuploidy was significantly more frequent in the translocation Down syndrome group, as compared with either complete trisomy 21 fetuses or normal controls. CONCLUSION: Fetuses with translocation Down syndrome present with the same screening abnormalities as fetuses with complete trisomy 21.

Technical standards and guidelines: prenatal screening for Down syndrome that includes first-trimester biochemistry and/or ultrasound measurements.

This statement is intended to augment the current general ACMG Standards and Guidelines for Clinical Genetics Laboratories and to address guidelines specific to first-trimester screening for Down syndrome. The aim is to provide the laboratory the necessary information to ensure accurate and reliable Down syndrome screening results given a screening protocol (e.g., combined first trimester and integrated testing). Information about various test combinations and their expected performance are provided, but other issues such as availability of reagents, patient interest in early test results, access to open neural tube defect screening, and availability of chorionic villus sampling are all contextual factors in deciding which screening protocol(s) will be selected by individual health care providers. Individual laboratories are responsible for meeting the quality assurance standards described by the Clinical Laboratory Improvement Act, the College of American Pathologists, and other regulatory agencies, with respect to appropriate sample documentation, assay validation, general proficiency, and quality control measures. These guidelines address first-trimester screening that includes ultrasound measurement and interpretation of nuchal translucency thickness and protocols that combine markers from both the first and second trimesters. Laboratories can use their professional judgment to make modification or additions.

Comparison of modes of ascertainment for mosaic vs complete trisomy 21.

OBJECTIVE: We sought to compare the indications for amniocentesis leading to the detection of either mosaicism of trisomy 21 (mosaic-T21) or complete trisomy 21 (T21). STUDY DESIGN: A retrospective review of a large amniocentesis database (n = 494,163) was conducted. All specimens with mosaic-T21 (n = 124) were compared with a maternal age-matched group of T21 fetuses (n = 496). Samples with normal karyotypes were matched for maternal age and served as normal controls (n = 496). The chi(2) testing was used for statistical analysis. RESULTS: The presence of an abnormal first-trimester screen, abnormal sonographic findings, and specifically the single sonographic abnormalities of either a cystic hygroma or a cardiac anomaly were significantly less common in the mosaic-T21 as compared with the T21 group. There were no such differences between the mosaic-T21 and the normal control group. CONCLUSION: Fetuses with mosaic-T21, similar to those with normal karyotype, do not present with the same abnormal screening tests as fetuses with T21.

Quality assessment of routine nuchal translucency measurements: a North American laboratory perspective.

PURPOSE: To assess nuchal translucency measurements that were performed as part of routine prenatal screening for Down syndrome. METHODS: Collect ultrasound measurements of nuchal translucency and crown rump length provided by individual sonographers over a 6-month period to six North American prenatal screening laboratories, along with the laboratory's nuchal translucency interpretation in multiples of the median. For sonographers with 50 or more observations, compute three nuchal translucency quality measures (medians, standard deviations, and slopes), based on epidemiological monitoring. RESULTS: Altogether, 23,462 nuchal translucency measurements were submitted by 850 sonographers. Among the 140 sonographers (16%) who submitted more than 50 observations, 76 (54%) were found to have all three quality measures in the target range. These 140 sonographers collectively accounted for 14,210 nuchal translucency measurements (61%). The most common single measure to be out of range was nuchal translucency multiples of the median, found for 29 of the 140 sonographers (21%). CONCLUSION: Laboratories should routinely monitor the quality of nuchal translucency measurements that are received for incorporation into Down syndrome screening risk calculations and interpretations. When possible, instituting sonographer-specific medians and providing individualized feedback about performance and numbers of women tested offer the potential to yield more consistent and improved performance.

Prevalence and instability of fragile X alleles: implications for offering fragile X prenatal diagnosis.

OBJECTIVE: To document fragile X allele frequencies in a national referral population and evaluate CGG repeat expansion in mother-offspring transmissions. METHODS: Fragile X DNA analysis by Southern blot and polymerase chain reaction was completed for 14,675 women, aged 18 years or older, and 238 mother-offspring pairs between January 1999 and June 2004. Carrier frequencies were compared between groups referred for different clinical indications. Direct comparison of the FMR1 gene CGG repeat size in mother-offspring pairs determined intermediate and premutation allele stability. RESULTS: Intermediate fragile X alleles (45-54 CGG repeats) occurred in 257 (1 in 57). The combined total number of patients with a premutation (55-200 CGG repeats) or full mutation (more than 200 CGG repeats) numbered 208 (1 in 71). One in 3.5 women with a family history of fragile X and 1 in 10 with premature ovarian failure had a FMR1 mutation. This compared with 1 in 86 for those with a family history of mental retardation and 1 in 257 for women with no known risk factors for fragile X. Among 238 mother-offspring pairings, the smallest allele to expand to a full mutation in one generation contained 60 CGG repeats. Although 6.6% (4 of 60) of intermediate repeat alleles did expand, none jumped to a clinically significant full mutation-sized allele. CONCLUSION: Based on these data and other published literature, offering invasive prenatal diagnosis for fragile X syndrome is not indicated for women with intermediate alleles. Invasive prenatal diagnosis is warranted for those women with a fragile X allele containing 55 or more CGG repeats.

The risk of a major trisomy in fetuses with pyelectasis: the impact of an abnormal maternal serum screen or additional sonographic markers.

OBJECTIVE: This study was undertaken to evaluate the contribution of either an abnormal second-trimester maternal serum screen or the presence of additional sonographic markers of aneuploidy to the risk of a major trisomy (13, 18, and 21) in fetuses with pyelectasis. STUDY DESIGN: A retrospective review of a large amniocentesis database was performed. Specimens obtained after the sonographic detection of fetal pyelectasis were eligible for analysis. Age-matched women who underwent amniocentesis solely for maternal anxiety or advanced maternal age served as controls. RESULTS: 760,495 amniocentesis specimens were analyzed. Fetal pyelectasis was detected in 671 cases. Pyelectasis, with either a single or multiple additional sonographic markers, was associated with an 8-fold and 62-fold increase in the prevalence of major trisomies (odds ratio = 7.7, 95% CI = 1.2-32.6, P = 0.02) and (odds ratio = 61.9, 95% CI = 13.2-144.6, P < .001), respectively. Pyelectasis with an abnormal maternal serum screen, with or without additional sonographic markers, was associated with a 32-fold and a 205-fold increase in major trisomies (odds ratio = 32.2, 95% CI = 5.3-94.8, P < .001) and (odds ratio = 205.8, 95% CI = 37.9-427.6, P < .001), respectively. CONCLUSION: In fetuses with pyelectasis, the presence of additional sonographic markers or an abnormal maternal serum screen significantly increases the risk of trisomy 13, 18, and 21.

Fetal pyelectasis: does fetal gender modify the risk of major trisomies?

OBJECTIVE: Several studies have noted an increased prevalence of pyelectasis in male fetuses. It is speculated that pyelectasis represents a normal physiologic variant in males, whereas its presence in females indicates an increased risk of chromosomal abnormalities. Thus, we sought to investigate the association between fetal gender and the risk of major trisomies in fetuses with pyelectasis. METHODS: Retrospective analysis of a Genzyme Genetics amniocentesis database (1995 to 2004) was performed. Specimens obtained after an ultrasonographic finding of pyelectasis were eligible for analysis. The prevalence of major trisomies (trisomy 13, 18, or 21) in male and female fetuses with pyelectasis was compared using binomial distribution. RESULTS: A total of 760,495 amniocentesis specimens were analyzed. Fetal pyelectasis was reported in 671 cases. A male predominance, with a male-to-female ratio of 2.14:1 (457 compared with 214) was statistically significant (P < .001). A major trisomy was detected in 26 male fetuses (5.7%): 18 cases of trisomy 21, 2 cases of trisomy 18, and 6 cases of trisomy 13. Nine female fetuses had a major trisomy (4.2%): 6 cases of trisomy 21 and 3 cases of trisomy 13. There was no significant difference in the overall prevalence of trisomies between male and female fetuses (P = .14). CONCLUSION: We concur with previous studies documenting a higher prevalence of pyelectasis in male fetuses. In addition, our results indicate that the prevalence of major trisomies among fetuses with pyelectasis is unlikely to be dependent on fetal gender. Thus, counseling patients with regard to the genetic implications of fetal pyelectasis should be gender independent. LEVEL OF EVIDENCE: II-2.

Prospective study of 22q11 deletion analysis in fetuses with excess nuchal translucency.

OBJECTIVE: The purpose of this study was to determine the frequency of 22q11 deletions (DiGeorge, velocardiofacial syndromes) in chromosomally normal fetuses with excess nuchal translucency. STUDY DESIGN: We evaluated chorionic villus sampling (CVS) samples submitted with an indication of excess nuchal translucency. If chromosome analysis was normal, permission was obtained to perform 22q11 microdeletion fluorescence in situ hybridization analysis. By Fisher exact test, the null hypothesis that there is no association between excess nuchal translucency and 22q11 deletions was tested. RESULTS: Among 239 CVS samples from fetuses with excess nuchal translucency, 93 (39%) were chromosomally abnormal. Of the remaining 146 specimens, 80 CVS samples were chromosomally normal, had documentation of nuchal translucency > 3.0 mm, and were included in the study at the referring obstetrician's request. None of the 80 fetuses with an increased nuchal translucency and normal karyotype demonstrated a 22q11 microdeletion. By Fisher exact test, the probability of 80 fetuses with excess nuchal translucency having no deletions of chromosome 22 was not significantly different than the expected rate of 0.18% (P value = 1). CONCLUSION: Routine 22q11 microdeletion analysis for fetuses with excess nuchal translucency is not indicated. Instead, we recommend storing an extra unbanded slide from the cultured CVS material to permit 22q11 FISH analysis should a cardiac malformation be identified later by fetal echocardiography.

Cytogenetics and molecular cytogenetics in prenatal diagnosis.

Prenatal chromosome diagnosis has been a rapidly changing field over the past 10 years for both sampling methodologies and molecular techniques to complement chromosome analysis. This review summarizes current techniques used by the clinician and their risks, and selected aspects of cytogenetic and molecular techniques used by the laboratories. Within the next 3 to 5 years, DNA techniques are expected to complement, and potentially replace, aspects of current cytogenetic and FISH techniques, and provide more detailed information on the genetic status of the fetus.

Moderately increased risks of Down's syndrome (1/51-1/270) identified on first trimester sequential screening: what do patients do with this information?

OBJECTIVE: To document patient decisions after being informed of a first trimester sequential screen Down's syndrome risk between 1/51 and 1/270. SETTING: A database analysis of sequential screen results for patients seen in the Philadelphia, PA (USA) area between January 2006 and March 2008 was examined. METHODS: All patients with first trimester sequential screen Down's syndrome risks in the 1/51-1/270 range were identified. Patient decisions regarding invasive testing (prior to completing the second trimester stage of the sequential screen), completion of the second trimester blood draw or no additional testing were tabulated. RESULTS: A total of 10,850 patients underwent first trimester sequential screening during this interval. Five hundred and fifty-seven patients (5.1%) met the study inclusion criteria and had risks between 1/51 and 1/270. Ninety-three percent of these patients completed the sequential screening process before making any decisions regarding invasive testing. Four percent did not elect an invasive prenatal diagnosis procedure, but also did not complete the second trimester sequential screening blood draw and only 3.2% elected an invasive procedure based on their first trimester risk without completing the second trimester blood draw. Five women (0.9%) with low risks after the second stage screen chose to have an amniocentesis. CONCLUSION: The vast majority (97%) of patients in the moderately increased Down's syndrome risk range (1/51-1/270) following first trimester sequential screening did not pursue an invasive procedure based on their first trimester sequential screen risk. Using a > or = 1/50 risk cut-off in the first trimester is an effective screening policy for sequential screening.

Maternal reactions to two-dimensional compared to three-dimensional foetal ultrasonography.

Our objective was to quantitatively compare maternal reactions to viewing a three-dimensional (3D) ultrasound image of the foetal face to a traditional two-dimensional (2D) sonographic image. One hundred and twelve pregnant women were asked to evaluate their excitement, relief, amazement and satisfaction reactions to 2D and 3D ultrasound images of their foetus' face. A weighted kappa Cochran-Armitage trend test, Fisher exact test and generalised estimating equations were used to analyse the data obtained. 3D imaging was found to result in significantly more favourable reactions than 2D imaging of the foetal face. 3D imaging was significantly better than 2D in regard to the clearness of the image, feeling closer to the baby, experiencing amazement and recognising specific facial features. We hypothesised that 3D images might evoke more feelings of fear than 2D, but our analysis found there were no significant differences in this regard. 3D ultrasonography of the foetal face is well received by patients. It has been shown in this study to elicit stronger and more positive maternal reactions regarding excitement, amazement and satisfaction than experienced with 2D ultrasound.

Advanced maternal age as a sole indication for genetic amniocentesis; risk-benefit analysis based on a large database reflecting the current common practice.

AIMS: Recent advances in prenatal screening, including first and second trimester genetic screening as well as targeted sonography, have significantly improved the detection of trisomy 21. Therefore, several investigators have questioned the validity of recommending genetic amniocentesis to all women who are 35 years or older at delivery. Thus, we sought to investigate the risks and benefits associated with performing genetic amniocentesis in women whose sole indication for testing was advanced maternal age (AMA). METHODS: A retrospective review of a Genzyme Genetics amniocentesis database (January 2006-December 2006) was performed. All specimens obtained from women of AMA as the sole indication were eligible for analysis. The amniocentesis-related potential fetal loss was calculated based on the traditional fetal loss rate of 1/200 as well as the recently published loss rate of 1/1600 procedures. Risk-benefit analysis was performed by comparing the number of trisomy 21 fetuses identified within the AMA group to the potential number of amniocentesis-related fetal losses within this group. RESULTS: A total of 87,241 amniocentesis specimens were processed during the study period. AMA was the sole indication for genetic amniocentesis in 43,303 cases which formed the study group. In 399 (0.92%) of these cases, a trisomy 21 was identified. Assuming an amniocentesis related fetal loss rates of 1/200 or 1/1600; 217 or 27 fetal losses would have been expected, respectively. CONCLUSIONS: Our analysis suggests that the benefit of genetic amniocentesis for the sole indication of AMA far outweighs the potential amniocentesis-related fetal loss rate, regardless of the actual rate one considers.

Characteristics and perspectives of families waiting to adopt a child with Down syndrome.

PURPOSE: The study's purpose was to obtain information on the characteristics and perspectives of families interested in adopting children with Down syndrome. METHODS: A questionnaire-based survey was administered to individuals and families on a waiting list to adopt children with Down syndrome. Information on (1) demographic, (2) family structure, (3) Down syndrome exposure, (4) Down syndrome knowledge, (5) reasons for considering adoption, (6) adoption process, and (7) perspective on raising children with Down syndrome was assessed. RESULTS: From 199 mailed surveys, there were 72 respondents (36.2%) of whom six had previously adopted a child with Down syndrome. Forty-eight percent learned of the possibility of adopting children with Down syndrome through the Internet, whereas only one respondent obtained this information from a medical professional. The primary reasons for considering adoption were that prospective adoptive families were equipped with the necessary resources and had previous positive experiences with individuals who have Down syndrome. CONCLUSIONS: Many families are eager to adopt children with Down syndrome. Interest in this option stems from having resources to care for these children and previous positive experiences with individuals with Down syndrome. Information regarding adoption was rarely obtained from health care providers. When counseling pregnant women diagnosed with a Down syndrome fetus, adoption should be discussed so that all options regarding pregnancy management may be explored.

Prenatal diagnosis of an unexpected interstitial 22q11.2 deletion causing truncus arteriosus and thymic hypoplasia in a ring 22 chromosome derived from a maternally inherited paracentric inversion.

OBJECTIVE: To present the prenatal diagnosis of an interstitial 22q11.2 deletion involving a ring 22 chromosome associated with truncus arteriosus and a hypoplastic thymus. CASE: Following the sonographic diagnosis of a cystic hygroma at 12 weeks of gestation, chromosome analysis revealed a ring 22 chromosome. RESULTS: Ring chromosomes typically result in the deletion of genetic material from the distal long and short arms of the affected chromosome. The presence of an interstitial deletion in a ring chromosome is therefore unusual. FISH analysis revealed an unexpected deletion involving the TUPLE1 gene in the DiGeorge/Velocardiofacial syndrome region in 22q11.2. Maternal chromosome analysis revealed the cause of the apparent interstitial deletion, a paracentric inversion in the long arm of chromosome 22, resulting in the distal long arm of 22q being located adjacent to the centromere and the proximal end being located near the telomere. The fetus was subsequently diagnosed with truncus arteriosus and a hypoplastic thymus, consistent with DiGeorge syndrome. CONCLUSION: The ring chromosome 22 found in the fetus appears to have been derived from a rearrangement of the mother's inverted 22, resulting in ring formation and loss of the end of the distal long arm of the inverted 22, including the TUPLE1 locus, causing DiGeorge syndrome in the fetus. The apparent interstitial deletion was actually a terminal deletion in a maternally inherited rearranged chromosome 22.

Sequential Down syndrome screening: the importance of first and second trimester test correlations when calculating risk.

Down syndrome screening can be particularly effective when both first and second trimester tests are performed. However, the counseling of women who have received sequential first and second trimester screening can be problematic. We evaluated an approximation where the post-test risk from the first trimester screening is used as the new a priori risk for the second trimester screening. The approximation disregards between-trimester test correlations. The Down syndrome detection rate based on the approximation (90.2%) would be close to that obtained when all correlations were considered (90.8%) but the false positive rate would be 26% higher (3.9% versus 3.1%, respectively). For any particular woman, the use of the approximation could result in highly inaccurate risks. We conclude that the correlations that exist between first and second trimester screening tests preclude the use of second trimester risks derived from the direct product of separate first and second trimester screening. Counseling issues in the delivery of sequential screening are discussed.

Chromosomal abnormalities among 246 fetuses with pleural effusions detected on prenatal ultrasound examination: factors associated with an increased risk of aneuploidy.

PURPOSE: To determine the prevalence of chromosomal abnormalities in fetuses with prenatally diagnosed pleural effusions and to identify factors associated with an increased risk of aneuploidy. METHODS: A retrospective analysis of the Genzyme Genetics database was performed for samples submitted from October 1994 to April 2003 with an indication of fetal pleural effusion. RESULTS: There were 246 samples in which pleural effusion was identified as an indication for prenatal chromosome analysis. Ninety-four were from fetuses with isolated pleural effusions and 152 had other abnormalities in addition to pleural effusion. The prevalence of chromosome abnormalities was 35.4% (95% confidence interval, 29.2-41.4%). Among the eight first trimester samples, the aneuploidy rate was 63%. Pleural effusion cases associated with additional sonographic findings had a significantly higher aneuploidy rate than the isolated pleural effusion cases (50% vs. 12%, P < 0.001). CONCLUSIONS: Chromosome analysis is warranted after the prenatal detection of a fetal pleural effusion. The risk of aneuploidy is greater with first trimester detection and is significantly increased in the presence of other associated anomalies.

Fragile X syndrome carrier screening in the prenatal genetic counseling setting.

PURPOSE: To document our experience with fragile X carrier screening. METHODS: In this study, 29,103 women with no known or suspected family history of fragile X syndrome were offered fragile X carrier screening during their prenatal genetic counseling visit. Screening acceptance was analyzed by referral indication, carrier frequencies documented, and prenatal outcome data presented. RESULTS: Overall, 7.9% accepted carrier screening. The premutation frequency was 1 in 382, and the intermediate allele frequency was 1 in 143. CONCLUSIONS: Fragile X screening is a desirable option for some women seeking prenatal genetic counseling and should be made available to this population.