Chorionic villus sampling and amniocentesis in 2008

Expansion of non-invasive prenatal screening to the screening of 10 types of chromosomal anomalies: a cost-effectiveness analysis

OBJECTIVES

To determine the cost-effectiveness of the addition of chromosomal anomalies detectable by non-invasive prenatal screening (NIPS), in a prenatal screening programme targeting common aneuploidies.

DESIGN, SETTING AND PARTICIPANTS

A simulation study was conducted to study the addition of chromosomal anomalies detectable by NIPS (sex chromosome aneuploidies, 22q11.2 deletion syndrome, large deletion/duplication >7 Mb and rare autosomal trisomies) to five basic strategies currently aiming the common trisomies: three strategies currently offered by the public healthcare systems in Canada, whose first-tier test is performed with biochemical markers, and two programmes whose first-tier test consists of NIPS-based methods.

OUTCOME MEASURES

The total number of cases of chromosomal anomalies detected and the costs related to the consumption of medical services.

RESULTS

The most effective and the most cost-effective option in almost all prenatal screening strategies is the option that includes all targeted additional conditions. In the strategies where NIPS is used as first-tier testing, the cost per additional case detected by adding all possible additional anomalies to a programme that currently targets only common trisomies is $C25 710 (95% CI $C25 489 to $C25 934) for massively parallel shotgun sequencing and $C57 711 (95% CI $C57 141 to $C58 292) for targeted massively parallel sequencing, respectively. The acceptability curves show that at a willingness-to-pay of $C50 000 per one additional case detected, the expansion of NIPS-based methods for the detection of all possible additional conditions has a 90% probability of being cost-effective.

CONCLUSION

From an economic perspective, in strategies that use NIPS as a first-tier screening test, expanding the programmes to detect any considered chromosomal anomalies other than the three common trisomies would be cost-effective. However, the potential expansion of prenatal screening programmes also requires consideration of societal issues, including ethical ones.

Decision aids that support decisions about prenatal testing for Down syndrome: an environmental scan

BACKGROUND

Prenatal screening tests for Down syndrome (DS) are routine in many developed countries and new tests are rapidly becoming available. Decisions about prenatal screening are increasingly complex with each successive test, and pregnant women need information about risks and benefits as well as clarity about their values. Decision aids (DAs) can help healthcare providers support women in this decision. Using an environmental scan, we aimed to identify publicly available DAs focusing on prenatal screening/diagnosis for Down syndrome that provide effective support for decision making.

METHODS

Data sources searched were the Decision Aids Library Inventory (DALI) of the Ottawa Patient Decision Aids Research Group at the Ottawa Health Research Institute; Google searches on the internet; professional organizations, academic institutions and other experts in the field; and references in existing systematic reviews on DAs. Eligible DAs targeted pregnant women, focused on prenatal screening and/or diagnosis, applied to tests for fetal abnormalities or aneuploidies, and were in French, English, Spanish or Portuguese. Pairs of reviewers independently identified eligible DAs and extracted characteristics including the presence of practical decision support tools and features to aid comprehension. They then performed quality assessment using the 16 minimum standards established by the International Patient Decision Aids Standards (IPDASi v4.0).

RESULTS

Of 543 potentially eligible DAs (512 in DALI, 27 from experts, and four on the internet), 23 were eligible and 20 were available for data extraction. DAs were developed from 1996 to 2013 in six countries (UK, USA, Canada, Australia, Sweden, and France). Five DAs were for prenatal screening, three for prenatal diagnosis and 12 for both). Eight contained values clarification methods (personal worksheets). The 20 DAs scored a median of 10/16 (range 6-15) on the 16 IPDAS minimum standards.

DISCUSSION

None of the 20 included DAs met all 16 IPDAS minimum standards, and few included practical decision support tools or aids to comprehension.

CONCLUSIONS

Our results indicate there is a need for DAs that effectively support decision making regarding prenatal testing for Down syndrome, especially in light of the recently available non-invasive prenatal screening tests.

Transcervical chorionic villus sampling: a practical guide

First trimester screening for fetal aneuploidies has made the implementation of diagnostic techniques essential. Chorionic villus sampling (CVS) is the method of choice for obtaining chorionic villi for molecular and cytogenetic analysis in the first trimester. Two techniques have been developed, a transcervical and a transabdominal. The selection criteria have been based historically on factors, such as placental location, parity, maternal weight and preference of the operator. In our institution, we developed an elevated level of expertise in the field of transcervical approach, resulting in good quality of samples and comparable fetal loss rate to other approaches. Despite three decades of transcervical CVS performance, little consensus in terms of its technique and clinical guidelines exists. Considering the expertise and the volume of procedures performed at our center, we suggest a practical clinical guideline for transcervical CVS.

Use of cell-free fetal DNA in maternal plasma for noninvasive prenatal screening

Noninvasive prenatal testing (NIPT) using cell-free fetal (cfDNA) offers potential as a screening tool for fetal anomalies. All pregnant women should be offered prenatal screening and diagnostic testing based on current guidelines. Adoption of NIPT in high-risk pregnancies suggests a change in the standard of care for genetic screening; there are advantages to an accurate test with results available early in pregnancy. This accuracy decreases the overall number of invasive tests needed for diagnosis, subjecting fewer pregnancies to the risks of invasive procedures. Women undergoing NIPT need informed consent before testing and accurate, sensitive counseling after results are available.

Short-term outcomes after second-trimester genetic amniocentesis in Siriraj Hospital

OBJECTIVE

To determine the short-term outcomes of second-trimester genetic amniocentesis at Siriraj Hospital, Bangkok, Thailand.

METHODS

In a retrospective descriptive study, data were assessed from women with a singleton pregnancy who underwent genetic amniocentesis between 16 and 21 gestational weeks at the Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Siriraj Hospital, from May 2007 to June 2012. The amniocentesis records and medical data of all women were analyzed statistically.

RESULTS

During the 5-year period, complete data were collected for 3307 pregnant women. The rate of total pregnancy loss within 4 weeks of testing was 7 out of 3307 (0.2%; 95% confidence interval, 0.1%-0.4%). Advanced maternal age (≥35 years) was the most common indication for amniocentesis (94.6%). The culture failure rate was 0.2%. Chromosomal abnormalities were detected in 109 pregnancies (3.3%); trisomy 21 was the most prevalent abnormality (0.8%). The possible risk factors of fetal loss were early amniocentesis (gestational age, <18 weeks) (P=0.013), abnormal fetal sonography (P=0.004), culture failure (P=0.015), and old-blood- or murky-stained amniotic fluid (P=0.036).

CONCLUSION

Second-trimester genetic amniocentesis resulted in 0.2% of total pregnancy loss within 4 weeks of testing. This information is essential for patient counseling before amniocentesis.

Recent advances in the prenatal interrogation of the human fetal genome

The amount of genetic and genomic information obtainable from the human fetus during pregnancy is accelerating at an unprecedented rate. Two themes have dominated recent technological advances in prenatal diagnosis: interrogation of the fetal genome in increasingly high resolution and the development of non-invasive methods of fetal testing using cell-free DNA in maternal plasma. These two areas of advancement have now converged with several recent reports of non-invasive assessment of the entire fetal genome from maternal blood. However, technological progress is outpacing the ability of the healthcare providers and patients to incorporate these new tests into existing clinical care, and further complicates many of the economic and ethical dilemmas in prenatal diagnosis. This review summarizes recent work in this field and discusses the integration of these new technologies into the clinic and society.

Non-invasive prenatal detection of trisomy 21 using tandem single nucleotide polymorphisms

Background

Screening tests for Trisomy 21 (T21), also known as Down syndrome, are routinely performed for the majority of pregnant women. However, current tests rely on either evaluating non-specific markers, which lead to false negative and false positive results, or on invasive tests, which while highly accurate, are expensive and carry a risk of fetal loss. We outline a novel, rapid, highly sensitive, and targeted approach to non-invasively detect fetal T21 using maternal plasma DNA.

Methods and Findings

Highly heterozygous tandem Single Nucleotide Polymorphism (SNP) sequences on chromosome 21 were analyzed using High-Fidelity PCR and Cycling Temperature Capillary Electrophoresis (CTCE). This approach was used to blindly analyze plasma DNA obtained from peripheral blood from 40 high risk pregnant women, in adherence to a Medical College of Wisconsin Institutional Review Board approved protocol. Tandem SNP sequences were informative when the mother was heterozygous and a third paternal haplotype was present, permitting a quantitative comparison between the maternally inherited haplotype and the paternally inherited haplotype to infer fetal chromosomal dosage by calculating a Haplotype Ratio (HR). 27 subjects were assessable; 13 subjects were not informative due to either low DNA yield or were not informative at the tandem SNP sequences examined. All results were confirmed by a procedure (amniocentesis/CVS) or at postnatal follow-up. Twenty subjects were identified as carrying a disomy 21 fetus (with two copies of chromosome 21) and seven subjects were identified as carrying a T21 fetus. The sensitivity and the specificity of the assay was 100% when HR values lying between 3/5 and 5/3 were used as a threshold for normal subjects.

Conclusions

In summary, a targeted approach, based on calculation of Haplotype Ratios from tandem SNP sequences combined with a sensitive and quantitative DNA measurement technology can be used to accurately detect fetal T21 in maternal plasma when sufficient fetal DNA is present in maternal plasma.

MALDI-TOF MS in Prenatal Genomics

Prenatal diagnosis aims either to provide the reassurance to the couples at risk of having an affected child by timely appropriate therapy or to give the parents a chance to decide the fate of the unborn babies with health problems. Invasive prenatal diagnosis (IPD) is accurate, however, carrying a risk of miscarriage. Non-invasive prenatal diagnosis (NIPD) has been developed based on the existing of fetal genetic materials in maternal circulation; however, a minority fetal DNA in majority maternal background DNA hinders the detections of fetal traits. Different protocols and assays, such as homogenous MassEXTEND (hME), single allele base extension reaction (SABER), precise measuring copy number variation of each allele, and quantitative methylation and expression analysis using the high-throughput sensitive matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), allow NIPD for single gene disorders, fetal blood group genotyping and fetal aneuploidies as well as the development of fetal gender-independent biomarkers in maternal circulation for management of pathological pregnancies. In this review, we summarise the use of MALDI-TOF MS in prenatal genomics.

Altered global gene expression in first trimester placentas of women destined to develop preeclampsia

BACKGROUND

Preeclampsia is a pregnancy-specific disorder that remains a leading cause of maternal, fetal and neonatal morbidity and mortality, and is associated with risk for future cardiovascular disease. There are no reliable predictors, specific preventative measures or treatments other than delivery. A widely held view is that the antecedents of preeclampsia lie with impaired placentation in early pregnancy. Accordingly, we hypothesized dysregulation of global gene expression in first trimester placentas of women who later manifested preeclampsia.

METHODS

Surplus chorionic villus sampling (CVS) tissues were collected at 10-12 weeks gestation in 160 patients with singleton fetuses. Four patients developed preeclampsia, and their banked CVS specimens were matched to 8 control samples from patients with unaffected pregnancies. Affymetrix HG-U133 Plus 2.0 GeneChips were utilized for microarray analysis. Naïve Bayes prediction modeling and pathway analysis were conducted. qRT-PCR examined three of the dysregulated genes.

RESULTS

Thirty-six differentially expressed genes were identified in the preeclampsia placentas. qRT-PCR verified the microarray analysis. Thirty-one genes were down-regulated. Many were related to inflammation/immunoregulation and cell motility. Decidual gene dysregulation was prominent. No evidence was found for alterations in hypoxia and oxidative stress regulated genes.

CONCLUSIONS

To our knowledge, this is the first study to show dysregulation of gene expression in the early placentas of women approximately 6 months before developing preeclampsia, thereby reinforcing a placental origin of the disorder. We hypothesize that placentation in preeclampsia is compromised in the first trimester by maternal and fetal immune dysregulation, abnormal decidualization, or both, thereby impairing trophoblast invasion. Several of the genes provide potential targets for the development of clinical biomarkers in maternal blood during the first trimester. Supplementary materials are available for this article via the publisher's online edition.