Early amniocentesis--a cytogenetic evaluation of over 1500 cases

Segmental duplications and monosomies are linked to in vitro developmental arrest

PURPOSE

To verify which genetic abnormalities prevent embryos to blastulate in a stage-specific time.

METHODS

A single center retrospective study was performed between April 2016 and January 2017. Patients requiring Preimplantation Genetic Testing for Aneuploidies (PGT-A) by Next Generation Sequencing (NGS) were included. All embryos were cultured in a time-lapse imaging system and single blastomere biopsy was performed on day 3 of development. Segmental duplications and deletions as well as whole chromosome monosomies and trisomies were registered. Embryo arrest was defined if the embryo failed to blastulate 118 h post-injection. A logistic regression model was applied using the time to blastulate as the response variable and the different mutations as explanatory variables. A p value < 0.05 was considered significant.

RESULTS

Of the 285 biopsied cleavage stage embryos, 103 (36.1%) were euploid, and 182 (63.9%) were aneuploid. There was a significant difference in the developmental arrest between euploid and aneuploid embryos (8.7% versus 42.9%; p = 0.0001). Segmental duplications and whole chromosome monosomies were found to have a significant effect on developmental arrest (p = 0.0163 and p = 0.0075), while trisomies and segmental deletions had no effect on developmental arrest. In case of segmental duplications, an increase of one extra segmental duplication increases the odd of arrest by 159%. For whole chromosome monosomies, the odd will only increase by 29% for every extra chromosomal monosomy. Both chromosomal abnormalities remained significant after adding age as an explanatory variable to the model (p = 0.014 and p = 0.009).

CONCLUSION

Day 3 cleavage stage embryos with segmental duplications or monosomies have a significantly decreased chance to reach the blastocyst stage.

Rapid-prenatal diagnosis through fluorescence in situ hybridization for preventing aneuploidy related birth defects

BACKGROUND AND OBJECTIVE:

Women with high-risk pregnancies are offered prenatal diagnosis through amniocentesis for cytogenetic analysis of fetal cells. The aim of this study was to evaluate the effectiveness of the rapid fluorescence in situ hybridization (FISH) technique for detecting numerical aberrations of chromosomes 13, 21, 18, X and Y in high-risk pregnancies in an Indian scenario.

MATERIALS AND METHODS:

A total of 163 samples were received for a FISH and/or a full karyotype for prenatal diagnosis from high-risk pregnancies. In 116 samples both conventional culture techniques for getting karyotype through G-banding techniques were applied in conjunction to FISH test using the AneuVysion kit (Abbott Molecular, Inc.), following standard recommended protocol to compare the both the techniques in our setup.

RESULTS:

Out of 116 patients, we got 96 normal for the five major chromosome abnormality and seven patients were found to be abnormal (04 trisomy 21, 02 monosomy X, and 01 trisomy 13) and all the FISH results correlated with conventional cytogenetics. To summarize the results of total 163 patients for the major chromosomal abnormalities analyzed by both/or cytogenetics and FISH there were 140 (86%) normal, 9 (6%) cases were abnormal and another 4 (2.5%) cases were suspicious mosaic and 10 (6%) cases of culture failure. The diagnostic detection rate with FISH in 116 patients was 97.5%. There were no false-positive and false-negative autosomal or sex chromosomal results, within our established criteria for reporting FISH signals.

CONCLUSION:

Rapid FISH is a reliable and prompt method for detecting numerical chromosomal aberrations and has now been implemented as a routine diagnostic procedure for detection of fetal aneuploidy in India.

The role of preimplantation genetic diagnosis in diagnosing embryo aneuploidy

PURPOSE OF REVIEW

Use of preimplantation genetic diagnosis to improve in-vitro fertilization outcomes is reviewed.

RECENT FINDINGS

Many embryos produced in vitro contain chromosomal abnormalities and have little potential for forming a viable pregnancy. The most commonly used method for preimplantation genetic diagnosis involves embryo biopsy on day 3 of development, followed by fluorescence in-situ hybridization analysis of 5-12 chromosomes. However, positive results have been more common with single-cell biopsy and the analysis of nine or more chromosomes, including 15, 16, 21, and 22. Comparative genomic hybridization, array-comparative genomic hybridization, and single-nucleotide polymorphism arrays analyze all chromosomes and, although technically demanding and requiring experience for successful use, improve the selection potential of preimplantation genetic diagnosis and minimize error rates. Recent data suggest that biopsy at the blastocyst stage may allow sampling of representative genetic material without compromising embryo viability. The optimal strategy for aneuploidy screening using preimplantation genetic diagnosis seems to be blastocyst biopsy at 5 days and comprehensive chromosome analysis (comparative genomic hybridization, array-comparative genomic hybridization, single-nucleotide polymorphism array).

SUMMARY

The use of preimplantation genetic diagnosis to assist the identification and preferential transfer of healthy euploid embryos should improve implantation rates, reduce miscarriages and trisomic offspring, and ultimately lead to an increase in live birth rates.

Technology requirements for preimplantation genetic diagnosis to improve assisted reproduction outcomes

Preimplantation genetic diagnosis has been proposed as a method to improve assisted reproduction technology outcomes, but different techniques have produced conflicting results. The use of appropriate techniques may provide positive outcomes.

Relationship between embryo quality and aneuploidies

Many high-grade embryos selected for transfer according to their morphological evaluation were detected to have chromosomal abnormalities after aneuploidy screening for infertility by preimplantation genetic diagnosis (PGD). The aim of this study was to detect if there is any correlation between embryo quality and genetic status. The chromosomal status of the day three embryos was studied by multicolour fluorescence in-situ hybridization for chromosomes 13, 18, 21, X and Y. PGD was performed on 132 patients for 1107 embryos. The correlation between embryo quality and aneuploidy was analysed. The analysis showed that a large proportion of normal embryos (50.7%, n = 280) were grade I. In addition, a considerably high proportion of aneuploid embryos (36.1%, n = 83) were evaluated as grade I. There was a significant relationship between PGD results and embryo grades (P = 0.001). Of the 69 polyploid embryos, 21.7% were grade I and 37.8% were grade II. Of the 83 haploid embryos, 27.8% were grade I and 34.9% were grade II. Euploidy was positively related to morphological grade of embryo (P = 0.001). It was also possible for chromosomally abnormal embryos to have a good developmental potential, and they could be selected for embryo transfer unless the PGD procedure was applied.

Risk factors for isolated talipes equinovarus in Western Australia, 1980-1994

A case-control study based on routinely collected data for a West Australian (WA) cohort of births born 1980-94 inclusive was used to identify potential risk factors for the foot deformity isolated talipes equinovarus. Race and sex were identified as risk factors and risk modifiers of the condition in WA infants. In comparison with their female counterparts, Aboriginal males were at greater risk of the deformity than Caucasian males (odd ratio [OR] 7.15, 95% confidence interval [CI] 2.68, 21.12 vs. OR 1.63, 95% CI 1.24, 2.15 respectively). Sex-specific risk estimates of the deformity showed that Aboriginal males were at more than four times the risk of Caucasian males (OR 4.27, 95% CI 2.30, 8.25 respectively), but the risk amongst Aboriginal females was not dissimilar to the risk amongst Caucasian females (OR 1.12, 95% CI 0.49, 2.45). Intrauterine constraint of the fetus was not found to be an important contributing factor to the deformity after accounting for the effect of all risk factors modelled in multivariable analyses. Indicators of intrauterine constraint including prolonged gestation, high infant birthweight, young maternal age (< 20 years) and breech presentation were not associated with excess numbers of isolated talipes equinovarus cases. Limited numbers of cases associated with other indicators of intrauterine constraint, including the specific categories of short maternal stature and a twin pregnancy prevented definitive conclusions regarding their association with the deformity. Improved data quality for gestational age estimates and oligohydramnios status are required before determining the prenatal risk impact of season of conception and of reduced amniotic fluid levels, respectively, on the occurrence of the deformity.

Preimplantation genetic diagnosis

Preimplantation genetic diagnosis is essentially an alternative to prenatal diagnosis, in which genetic testing is performed on embryos before a clinical pregnancy is established. Preimplantation genetic diagnosis has been applied to patients carrying chromosomal rearrangements, such as translocations, in which it has been proven to decrease the number of spontaneous abortions and prevent the birth of children affected with chromosome imbalance. Preimplantation genetic diagnosis techniques have also been applied to increase implantation rates, reduce the incidence of spontaneous abortion and prevent trisomic offspring in women of advanced maternal age undergoing fertility treatment. A third group of patients receiving preimplantation genetic diagnosis are those at risk of transmitting a single gene disorder to their children. The number of monogenic disorders that have been diagnosed in preimplantation embryos has increased each year. Recent protocols have tended to be more complex and more reliable than previous methods, making greater use of multiplex polymerase chain reaction. As well as an expansion in the variety of disorders for which preimplantation genetic diagnosis is offered, new indications have been reported including the use of human leukocyte antigen histocompatibility typing and the application of preimplantation genetic diagnosis to late onset diseases.

Preimplantation genetic diagnosis of numerical and structural chromosome abnormalities

The causes of the decline in implantation rates observed with increasing maternal age are still a matter for debate. Data from oocyte donation strongly suggest that in women of advanced reproductive age, the ability to become pregnant is largely unaffected while oocyte quality is compromised. The incidence of chromosomal abnormalities in embryos is considerably higher than that reported in spontaneous abortions, suggesting that a sizable percentage of chromosomally abnormal embryos are eliminated before any prenatal diagnosis. Such loss may partly account for the decline in implantation in older women. Because of the correlation between aneuploidy and reduced implantation, it has been postulated that selection of chromosomally normal embryos could reverse this trend. Preimplantation genetic diagnosis (PGD) for aneuploidy had three objectives relevant to the present paper: (i) to increase rates of implantation, (ii) to reduce risks of spontaneous abortion, and (iii) to avoid chromosomally abnormal births. Implantation rates did not increase when only five chromosomes were analysed in blastomeres. With eight chromosomes, a significant increase in implantation was achieved. PGD can significantly reduce the incidence of spontaneous abortion. In our clinic, a significant decrease in spontaneous abortions was found, from 23 to 11% after PGD. Currently in cases diagnosed at Saint Barnabas, 0.8% chromosomally abnormal conceptions have been observed after PGD versus an expected 3.2% in a control age-matched group. It seems clear that PGD reduces the possibility of trisomic conceptions under all conditions. If a couple's main interest is to improve their chances of conceiving (improve implantation), then one should consider maternal age and number of available embryos. Improvements in conception after PGD again increase after 37 years of age with eight or nine probes. Carriers of translocations are at a high risk of miscarriage or chromosomally unbalanced offspring, and a high proportion have secondary infertility. PGD of translocations has been approached through a variety of methods, here reviewed, and has resulted in a significant reduction in spontaneous abortions. However, implantation rates in translocation carriers are directly correlated with the proportion of normal gametes, and male patients with 70% or more unbalanced spermatozoa have great difficulty in achieving pregnancy with PGD.

Developmental ability of chromosomally abnormal human embryos to develop to the blastocyst stage

BACKGROUND

A correlation between morphology, developmental competence and chromosome abnormalities is established. However, since absolute correlations are rare, embryo selection remains one of the most arduous tasks in assisted reproduction. This study was undertaken in order to determine which chromosomal abnormalities are compatible with development to the blastocyst stage.

METHODS

Embryos diagnosed by preimplantation genetic diagnosis (PGD) as chromosomally abnormal or unsuitable for transfer were cultured to day 5 or 6. Morphology and development were observed daily. After extended culture, embryos were fixed and analysed by two rounds of FISH with the same probes used for PGD.

RESULTS

Some types of numerical chromosome abnormalities do not preclude full differentiation in vitro. For instance, extensive mosaicism was detected in blastocysts and trisomic embryos reached the blastocyst stage with a frequency of 37%. Interestingly, only those monosomies compatible with first trimester development (monosomy X and 21) were detected at blastocyst stage.

CONCLUSION

Even though there is a strong selection against chromosomally abnormal embryos, extended culture to day 5 or 6 cannot be used as a reliable tool to select against clinically relevant chromosome abnormalities such as trisomies.

First trimester prenatal diagnosis: amniocentesis

Twenty years after midtrimester genetic amniocentesis was first used, first trimester invasive prenatal procedures were introduced. Chorionic villous sampling presents some disadvantages that entitled many centers to look into an alternative for first trimester diagnosis. Early amniocentesis (EA) can be performed effectively, as shown over the years in many observational studies and partially randomized and randomized trials. Recently, a multicenter randomized trial (Canadian Early and Midtrimester Amniocentesis Trial) reported a higher total pregnancy loss, a significant increased incidence of musculoskeletal foot deformities, a significant increased culture failure rate, and an increased postamniocentesis rate of leakage in the EA group compared with midtrimester amniocentesis. These results concerning EA procedures from 11w(+0) to 12w(+6) should be included in any pre-EA counseling. However, further trials have started to evaluate EA procedures between 13w(+0) to 14w(+6).

Cytogenetic aspects of the Canadian early and mid-trimester amniotic fluid trial (CEMAT)

Cytogenetic results from a large multicentre randomized controlled study of 2108 amniotic fluids obtained at 11+0-12+6 weeks (EA) and 1999 fluids at 15+0-16+6 weeks (MA) were compared. There was no statistically significant difference in the rate of chromosome abnormalities (EA =1.9 per cent; MA=1.7 per cent) or level III mosaicism (EA=0.2 per cent; MA= 0.2 per cent) between the groups. Level I and Level II mosaicism occurred more frequently in MA. Maternal cell contamination was not significantly different between the groups, but maternal cells only were analysed from one bloody EA fluid. The number of repeat amniocenteses because of cytogenetic problems was 2.2 per cent in the EA group compared with only 0.3 per cent in the MA group. On average, culture of EA fluids required one day more than MA fluids. Although both culture success (97.7 per cent) and accuracy (99.8 per cent) were high for patients randomized to the EA group, routine amniocentesis prior to 13 weeks' gestation is not recommended for clinical reasons including an increased risk of fetal loss and talipes equinovarus.

Transplacental early amniocentesis and pregnancy outcome

The effect on pregnancy outcome of transplacental needle insertion was studied in 401 consecutive women attending for early amniocentesis between 10 and 14 completed weeks of pregnancy. Transplacental early amniocentesis was associated with a significantly higher incidence (P < 0.001) of blood-stained amniotic fluid taps but a lower incidence (not significant; P > 0.05) of pregnancy loss and miscarriages. Women in the nontransplacental early amniocentesis group had a significantly higher (P < 0.01) incidence of late procedure-related antenatal complications, such as preterm rupture of membranes or preterm labour. Our study showed that transplacental early amniocentesis is a safe procedure; contrary to present recommendations, the study also showed that avoiding the placenta during early amniocentesis is an unnecessary practice.

Double-monoclonal immunofluorometric assays for pregnancy-associated plasma protein A/proeosinophil major basic protein (PAPP-A/proMBP) complex in first-trimester maternal serum screening for Down syndrome

Four double-monoclonal time-resolved immunofluorometric assays (TrIFMAs) have been developed for the specific determination of pregnancy-associated plasma protein A/proeosinophil major basic protein (PAPP-A/proMBP) complex in first-trimester maternal serum samples. The assays have a functional sensitivity of &lt;4 mIU/L and a working range from 4 to 1000 mIU/L. These 4 assays, together with a polyclonal sandwich TrIFMA, were compared for their ability to discriminate between normal pregnancies (n = 149) and pregnancies carrying a Down syndrome fetus (n = 36) in maternal serum screening samples from gestational weeks 4–13. In 26 Down syndrome pregnancies from gestational weeks 7–12, the median PAPP-A multiples of the median concentration in controls (MoMs) determined by monoclonal antibody combinations 234–3/234–2*, 234–4/234–2*, 234–4/234–5*, and 234–5/234–6* were 0.35, 0.37, 0.42, and 0.44, respectively, whereas the median MoM determined by the polyclonal assay was 0.56. ROC curve analysis also showed that better overall diagnostic accuracy and detection rates were achieved by the monoclonal TrIFMAs than by the polyclonal TrIFMA. This report is the first to describe assays that specifically measure PAPP-A/proMBP complex without possible interference from other proMBP-containing complexes.

Early amniocentesis at 10-12 weeks' gestation

In this study we report the results of 181 ultrasound-guided genetic amniocenteses performed at 10-12 weeks of gestation and describe the indication, technical problems, amniotic fluid volume, culture success and timing, abortion and fetal loss rate, and perinatal results. Amniotic fluid was obtained in 98.4 per cent of the cases; at the first attempt, in 167 out of 181. The culture success rate was 94.5 per cent, and the fetal loss rate within 2 weeks was 0.5 per cent (one case with a sonographic abnormality). The total fetal loss rate during pregnancy was 1.6 per cent. A comparison of our data and those of other published series shows no significant differences, either with respect to this period of gestation (10-12 weeks) or with respect to the traditionally called early amniocentesis' (12-14 weeks) or conventional amniocentesis (15 weeks or more). The mean culture time was just a few days longer in some of the series, and in some cases, there was also a lower success rate after culture, particularly when amniocentesis was carried out at 10 weeks or less. We conclude that amniocentesis performed at 10-12 weeks is feasible, safe, and easy to perform, and provides a real benefit to the pregnant woman.

Early amniocentesis: a clinical review

Early amniocentesis at less than 14 weeks gestation is becoming more common in prenatal diagnosis populations. Randomized studies are minimal and have not had the power to determine the accuracy and safety of the procedure compared to chorionic villus sampling or mid-trimester amniocentesis. Procedures at 11+0-12+6 weeks should be considered experimental. This clinical review considers the ethics, embryology, and clinical experience (cytogenetics, AFP, AChE, procedure and cytogenetic failures, spontaneous and therapeutic pregnancy losses, congenital anomalies) of early amniocentesis.