The role of preimplantation genetic diagnosis in diagnosing embryo aneuploidy

Is there an optimal window of time for transferring single frozen-thawed euploid blastocysts? A cohort study of 1170 embryo transfers

STUDY QUESTION

Is there an optimal window of time when the transfer of single frozen-thawed euploid blastocysts is associated with a maximal live birth rate (LBR)?

SUMMARY ANSWER

Performing a single frozen-thawed euploid blastocyst transfer at 160 ± 4 h post-hCG trigger in modified-natural frozen-thawed embryo transfer (FET) cycles was independently associated with a higher LBR as compared to transfers outside this window; however, in natural FET cycles, LBRs were comparable across a wider range of time intervals.

WHAT IS KNOWN ALREADY

There is compelling evidence for maintaining embryo-endometrial synchrony to optimize clinical outcomes following FETs, which could potentially be achieved by matching the transfer time of an embryo post-ovulation to its developmental age post-oocyte retrieval. For modified-natural cycles, ovulation is widely accepted to occur ∼40 h following the hCG trigger, whilst ovulation following spontaneous LH surge onset is thought to vary from 24 to 56 h.

STUDY DESIGN, SIZE, DURATION

This is a multicentered retrospective cohort study analyzing 1170 single frozen-thawed euploid blastocyst transfers following trophectoderm biopsy and preimplantation genetic testing (PGT) between May 2015 and February 2019. Limiting the analysis to single euploid embryo transfers allowed for a more accurate estimation of the endometrial synchrony factor by controlling for the developmental stage of the embryo (full blastocyst or more advanced) and its genetic composition. LBR per FET was the primary outcome measure.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients underwent natural or gonadotrophin-induced preparation of the endometrium, with serial serum oestradiol, LH and progesterone measurements. Optimally timed transfers were predefined as those conducted 120 ± 4 h post-ovulation since biopsy and subsequent cryopreservation of full blastocysts which is usually performed at 116-124 h post-oocyte retrieval. This was considered the equivalent of 160 ± 4 h post-hCG trigger in modified-natural cycles (n = 253), as ovulation was assumed to occur ∼40 h after the hCG trigger. For natural cycles (n = 917), this was also considered to be, on average, 160 ± 4 h post the spontaneous LH surge. Thus, study groups were determined as those with optimal timing or not, and additional exploratory and subgroup analyses were performed, varying the time window in terms of onset and width, both overall and per endometrial preparation protocol. Statistical analysis was performed using the generalized estimating equations (GEE) framework to control for the clustered nature of the data while adjusting for potential confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, LBRs were significantly higher when the transfer had been performed at 160 ± 4 h post-hCG trigger or LH surge onset compared to when it had been performed outside this window (44.7% vs 36.0%; P = 0.008). A multivariable regression GEE model including the cycle type (natural versus modified-natural), previtrification embryo quality (top versus good quality), embryo stage (fully hatched versus hatching or earlier blastocyst), vitrification day (D5 versus D6) and survival rate (>90% versus <90%) as covariates, confirmed that, overall, embryo transfers conducted 160 ± 4 h post-hCG trigger or LH surge onset (the assumed equivalent of 120 ± 4 h post-ovulation) were associated with a significantly higher LBR (relative risk (RR) 1.21, 95% CI 1.04-1.41). Subgroup exploratory analyses per endometrial preparation protocol demonstrated that these findings were primarily present in the modified-natural cycle group (RR 1.52, 95% CI 1.15-1.99), whilst the natural cycle group showed comparable LBRs across a wider range of time intervals. Moreover, the overall LBR for the natural group (36.8%; 95% CI 33.7-39.9%) was lower than that of the modified-natural group (41.3%; 95% CI 35.4-47.1%), suggesting that there likely remains a greater potential to further optimize the timing of natural cycle embryo transfers.

LIMITATIONS, REASONS FOR CAUTION

As with all retrospective studies, the presence of residual unknown bias cannot be excluded. Additionally, patients included in this study were a selected group who underwent PGT for specific reasons and hence the results obtained might not be directly applicable to the general population or embryos that have not undergone embryo biopsy. Furthermore, the criteria utilized to interpret hormonal data from natural cycles were specifically adopted for the present study and need to be validated in further studies.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study highlight the significance of embryo-endometrial synchrony for the optimization of frozen embryo transfer outcome. However, it also clearly supports that the implantation window is in most cases wide and the achievement of live birth is possible with relatively high success rates even outside the optimal window of 160 ± 4 h post-trigger for modified-natural cycles and across a range of time intervals for natural cycles. Additionally, this study suggests that implantation rates could be further optimized in natural cycles by improving methods of assessing embryo-endometrial synchrony.

STUDY FUNDING/COMPETING INTEREST(S)

C. V. is supported by a National Health and Medical Research Council Early Career Fellowship (GNT1147154). No other funding was received for this study and there are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

ChromInst: A single cell sequencing technique to accomplish pre-implantation comprehensive chromosomal screening overnight

Next Generation Sequencing (NGS) is a powerful tool getting into the field of clinical examination. Its preliminary application in pre-implantation comprehensive chromosomal screening (PCCS) of assisted reproduction (test-tube baby) has shown encouraging outcomes that improves the success rate of in vitro fertilization. However, the conventional NGS library construction is time consuming. In addition with the whole genome amplification (WGA) procedure in prior, makes the single cell NGS assay hardly be accomplished within an adequately short turnover time in supporting fresh embryo implantation. In this work, we established a concise single cell sequencing protocol, ChromInst, in which the single cell WGA and NGS library construction were integrated into a two-step PCR procedure of ~ 2.5hours reaction time. We then validated the feasibility of ChromInst for overnight PCCS assay by examining 14 voluntary donated embryo biopsy samples in a single sequencing run of Miseq with merely 13M reads production. The good compatibility of ChromInst with the restriction of Illumina sequencing technique along with the good library yield uniformity resulted superior data usage efficiency and reads distribution evenness that ensures precisely distinguish of 6 normal embryos from 8 abnormal one with variable chromosomal aneuploidy. The superior succinctness and effectiveness of this protocol permits its utilization in other time limited single cell NGS applications.

The Relationship between Sperm Oxidative Stress Alterations and IVF/ICSI Outcomes: A Systematic Review from Nonhuman Mammals

Achieving high embryo quality following IVF and ICSI procedures is a key factor in increasing fertility outcomes in human infertile couples. While the male factor is known to underlie infertility in about 50% of cases, studies performed in human infertile couples have not been able to define the precise effect of sperm affectations upon embryo development. This lack of consistency is, in most cases, due to the heterogeneity of the results caused by the multiple male and female factors that mask the concrete effect of a given sperm parameter. These biases can be reduced with the use of animal gametes, being a good approach for basic researchers to design more homogeneous studies analyzing the specific consequences of a certain affectation. Herein, we conducted a systematic review (March 2020) that assessed the relationship between sperm oxidative stress alterations and IVF/ICSI outcomes in nonhumans mammals. The review was conducted according to PRISMA guidelines and using the MEDLINE-PubMed and EMBASE databases. Thirty articles were included: 11 performed IVF, 17 conducted ICSI, and two carried out both fertilization methods. Most articles were conducted in mouse (43%), cattle (30%) and pig models (10%). After IVF treatments, 80% of studies observed a negative effect of sperm oxidative stress on fertilization rates, and 100% of studies observed a negative effect on blastocyst rates. After ICSI treatments, a positive relationship of sperm oxidative stress with fertilization rates (75% of studies) and with blastocyst rates (83% of studies) was found. In conclusion, the present systematic review shows that sperm oxidative stress is associated with a significant reduction in fertilization rates and in vitro embryo development.

Mapping allele with resolved carrier status of Robertsonian and reciprocal translocation in human preimplantation embryos

Reciprocal translocations (RecT) and Robertsonian translocations (RobT) are among the most common chromosomal abnormalities that cause infertility and birth defects. Preimplantation genetic testing for aneuploidy using comprehensive chromosome screening for in vitro fertilization enables embryo selection with balanced chromosomal ploidy; however, it is normally unable to determine whether an embryo is a translocation carrier. Here we report a method named "Mapping Allele with Resolved Carrier Status" (MaReCs), which enables chromosomal ploidy screening and resolution of the translocation carrier status of the same embryo. We performed MaReCs on 108 embryos, of which 96 were from 13 RecT carriers and 12 were from three RobT carriers. Thirteen of the sixteen patients had at least one diploid embryo. We have confirmed the accuracy of our carrier status determination in amniotic fluid karyotyping of seven cases as well as in the live birth we have thus far. Therefore, MaReCs accurately enables the selection of translocation-free embryos from patients carrying chromosomal translocations. We expect MaReCs will help reduce the propagation of RecT/RobT in the human population.

Assessment of clinical application of preimplantation genetic screening on cryopreserved human blastocysts

BACKGROUND

Recent advancement in both human embryology and preimplantation genetic screening has created a completely new situation for human assisted reproduction. Embryos, typically at blastocyst stage, are biopsied and screened by DNA microarray or next-generation sequencing before cryopreservation, and then euploid embryos are warmed for transfer. Increased embryo implantation rates have been reported after transfer of euploid embryos screened for all chromosomes. However, some patients may have frozen their embryos without doing embryo biopsy and screening, thus embryo biopsy and screening may be required after cryopreservation and warming. Such procedures have not been performed routinely in clinics and the efficiency is still unknown. Therefore, in this study, we investigated embryo implantation after blastocysts were cryopreserved/warmed, and then biopsied and screened by DNA microarray for all chromosomes.

RESULTS

Two hundred and thirty four cryopreserved blastocysts from 35 women were warmed, and 224 (95.7 %) survived and were biopsied for aneuploidy screening. After analysis, 221 samples (98.7 %) had diagnostic results and 3 (1.3 %) samples did not have results due to DNA quality and quantity. Out of the samples with diagnostic results, 59.3 % were normal euploid and 40.7 % had abnormal chromosomes including aneuploidy, partial chromosome deletion and/or duplication. Most (65.6 %) samples had single chromosome anomalies, and 34.4 % of the samples had multiple chromosome anomalies. Chromosomal errors were observed in most chromosomes but chromosomes 21 and 22 had the most frequent chromosome anomalies. Transfer of 61 normal euploid blastocysts in 34 patients resulted in a 52.9 % clinical pregnancy rate and a 42.6 % implantation rate, and 41.2 % of the patients delivered normal babies or had ongoing pregnancy.

CONCLUSIONS

Frozen blastocysts can be warmed and biopsied for aneuploidy screening. These results may suggest that cryopreserved blastocysts can be warmed, biopsied and screened the day before embryo transfer, and such procedures may benefit patients who had previous implantation failures, or patients who did not have embryo screening before cryopreservation due to lack of embryo screening technology or other reasons.

Bioinformatic Tools Identify Chromosome-Specific DNA Probes and Facilitate Risk Assessment by Detecting Aneusomies in Extra-embryonic Tissues

Despite their non-diseased nature, healthy human tissues may show a surprisingly large fraction of aneusomic or aneuploid cells. We have shown previously that hybridization of three to six non-isotopically labeled, chromosome-specific DNA probes reveals different proportions of aneuploid cells in individual compartments of the human placenta and the uterine wall. Using fluorescence in situ hybridization, we found that human invasive cytotrophoblasts isolated from anchoring villi or the uterine wall had gained individual chromosomes. Chromosome losses in placental or uterine tissues, on the other hand, were detected infrequently. A more thorough numerical analysis of all possible aneusomies occurring in these tissues and the investigation of their spatial as well as temporal distribution would further our understanding of the underlying biology, but it is hampered by the high cost of and limited access to DNA probes. Furthermore, multiplexing assays are difficult to set up with commercially available probes due to limited choices of probe labels. Many laboratories therefore attempt to develop their own DNA probe sets, often duplicating cloning and screening efforts underway elsewhere. In this review, we discuss the conventional approaches to the preparation of chromosome-specific DNA probes followed by a description of our approach using state-of-the-art bioinformatics and molecular biology tools for probe identification and manufacture. Novel probes that target gonosomes as well as two autosomes are presented as examples of rapid and inexpensive preparation of highly specific DNA probes for applications in placenta research and perinatal diagnostics.

Chromosome-specific DNA repeats: rapid identification in silico and validation using fluorescence in situ hybridization

Chromosome enumeration in interphase and metaphase cells using fluorescence in situ hybridization (FISH) is an established procedure for the rapid and accurate cytogenetic analysis of cell nuclei and polar bodies, the unambiguous gender determination, as well as the definition of tumor-specific signatures. Present bottlenecks in the procedure are a limited number of commercial, non-isotopically labeled probes that can be combined in multiplex FISH assays and the relatively high price and effort to develop additional probes. We describe a streamlined approach for rapid probe definition, synthesis and validation, which is based on the analysis of publicly available DNA sequence information, also known as “database mining”. Examples of probe preparation for the human gonosomes and chromosome 16 as a selected autosome outline the probe selection strategy, define a timeline for expedited probe production and compare this novel selection strategy to more conventional probe cloning protocols.

Lessons from elective in vitro fertilization (IVF) in, principally, non-infertile women

BACKGROUND

We here report the first investigation of exclusively elective in vitro fertilization (IVF) cycles in women with no apparent history of infertility. Since IVF outcome in women with infertility are always influenced by underlying causes of infertility, a study on non-infertile women may offer new insights.

METHODS

We investigated 88 females without history of infertility in 109 consecutive elective IVF cycles, almost exclusively performed for purposes of preimplantation genetic screening (PGS; i.e., elective gender selection). The following questions were addressed: (i) impact of PGS on IVF pregnancy chances; (ii) impact of transfer of 1 vs. ≥2 embryos on IVF pregnancy chances; (iii) correlation of anti-Müllerian hormone (AMH) levels to embryo ploidy (iv) effect of gonadotropin dosage used in stimulation on available embryos for transfer; and (v) in form of a 1:1 case control study, compared 33 elective PGS cycles with matched control cycles without PGS, performed in couples with either prior tubal ligations and/or severe male factor infertility as indication of IVF.

RESULTS

The overall clinical pregnancy rate for the group was 36.7%; pregnancy was associated with number of euploid (P = 0.009) and number of embryos transferred (P = 0.001). Odds of pregnancy were 3.4-times higher if ≥4 euploid embryos were produced in comparison to <4 (95% CI 1.2 to 9.2; P = 0.019), and odds of pregnancy were 6.6-times higher if greater than or equal to 2 rather than <1 euploid embryos were transferred (95% CI 2.0 to 21.7; P = 0.002). Increasing AMH (P = 0.001) and gonadotropin dosage used in ovarian stimulation (P = 0.024), was, independently, associated with number of available euploid embryos. Increasing AMH, but not follicle stimulating hormone (FSH), was associated with number of embryos available for biopsy and PGS (P = 0.0001). Implantation rates were 26.4% with PGS and 9.5% without (P = 0.008). Women undergoing PGS, demonstrated 4.58-times higher odds of pregnancy than matched controls (95% CI 1.102 to 19.060, Exp 4.584, P = 0.036).

CONCLUSIONS

This study suggests that outcomes of elective IVF cycles may significantly deviate from infertility-associated cycles. Affirming proof of concept for PGS, utilizing day-3 embryo biopsy and fluorescence in-situ hybridization (FISH), both widely held responsible for earlier failures to establish such proof, suggests that the principal cause of prior failures were likely not insufficient laboratory techniques but poor patient selection for PGS. Such a conclusion questions the current reintroduction of PGS with improved techniques and technologies in absence of prior determination of suited patient populations.

An update of preimplantation genetic diagnosis in gene diseases, chromosomal translocation, and aneuploidy screening

Preimplantation genetic diagnosis (PGD) is gradually widely used in prevention of gene diseases and chromosomal abnormalities. Much improvement has been achieved in biopsy technique and molecular diagnosis. Blastocyst biopsy can increase diagnostic accuracy and reduce allele dropout. It is cost-effective and currently plays an important role. Whole genome amplification permits subsequent individual detection of multiple gene loci and screening all 23 pairs of chromosomes. For PGD of chromosomal translocation, fluorescence in-situ hybridization (FISH) is traditionally used, but with technical difficulty. Array comparative genomic hybridization (CGH) can detect translocation and 23 pairs of chromosomes that may replace FISH. Single nucleotide polymorphisms array with haplotyping can further distinguish between normal chromosomes and balanced translocation. PGD may shorten time to conceive and reduce miscarriage for patients with chromosomal translocation. PGD has a potential value for mitochondrial diseases. Preimplantation genetic haplotyping has been applied for unknown mutation sites of single gene disease. Preimplantation genetic screening (PGS) using limited FISH probes in the cleavage-stage embryo did not increase live birth rates for patients with advanced maternal age, unexplained recurrent abortions, and repeated implantation failure. Polar body and blastocyst biopsy may circumvent the problem of mosaicism. PGS using blastocyst biopsy and array CGH is encouraging and merit further studies. Cryopreservation of biopsied blastocysts instead of fresh transfer permits sufficient time for transportation and genetic analysis. Cryopreservation of embryos may avoid ovarian hyperstimulation syndrome and possible suboptimal endometrium.

Autologous embryo–cumulus cells co-culture and blastocyst transfer in repeated implantation failures: a collaborative prospective randomized study

In repeated implantation failure, the co-culture of human embryos with somatic cells has been reported to promote the improvement of embryos quality, implantation and pregnancy rate. It was reported that feeder cells can be more beneficial to the oocyte and embryo by detoxifying the culture medium and supporting embryo development via different pathways. In this study, 432 patients, each with a minimum of three repeated implantation failures, were accepted for a prospective randomized study with or without autologous cumulus cell embryo co-culture and transfer at day 3 or day 5–6. We also investigated the expression of leukaemia inhibitor factor (LIF) and platelet activating factor receptor (PAF-R) on day 3 confluent cumulus cells. The statistic analysis of the data showed significant difference of implantation and clinical pregnancy rates between classical culture and day 3 compared with co-culture and day 5–6 transfer. The molecular analysis showed that cumulus cells express the LIF and the PAF-R genes and confirmed the possible positive role of growth factors and cytokines in early embryo development. Embryo co-culture systems with autologous cells can be beneficial in routine in vitro fertilization for embryo selection and implantation improvement. More molecular investigations need to be done to improve elucidation of the complex dialogue between the embryo and feeder cells prior to implantation and to understand the involved biological function and molecular process during embryo development.

First successful pregnancy following PGD for chromosome translocation on embryos generated from in-vitro matured oocytes: a case report

As far as is known, this is the first report of a successful pregnancy outcome following preimplantation genetic diagnosis for a chromosome translocation in embryos generated from in-vitro matured oocytes. A couple presented to the study clinic where the female partner was a carrier of the reciprocal chromosome translocation 46,XX,t(1;20)(p36.1;p12.2) with three consecutive pregnancy terminations due to either fetal abnormality or unbalanced translocation products detected in the conceptus. Under routine ultrasound investigation she was diagnosed with polycystic ovaries. The patient underwent an in-vitro maturation/preimplantation genetic diagnosis cycle where the immature oocytes were matured in vitro and fertilized by intracytoplasmic sperm injection. Day-3 embryos were screened for the chromosome abnormality by fluorescent in-situ hybridization. A single embryo diagnosed as chromosomally normal/balanced was transferred on day 5 and resulted in the birth of a healthy child.

Preimplantation genetic diagnosis at 20 years

First reported in 1990, PGD has evolved into a complementary form of prenatal diagnosis offering novel indications. DNA for PGD can be recovered with equal safety and facility from polar bodies I and II, blastomere (8 cell embryo) and trophectoderm (5-6 day blastocyst). Diagnostic accuracy is very high (>99%) for both chromosomal abnormalities and single gene disorders. Traditional application of FISH with chromosome specific probes for detecting aneuploidy and translocations may be replaced or complemented by array comparative genome hybridization (array CGH); biopsied embryos can now be cryopreserved (vitrification) while analysis proceeds in orderly fashion. PGD has been accomplished for over 200 different single gene disorders. Novel indications for PGD not readily applicable by traditional prenatal genetic diagnosis include avoiding clinical pregnancy termination, performing preconceptional diagnosis (polar body I), obtaining prenatal diagnosis without disclosure of prenatal genotype (nondisclosure), diagnosing adult-onset disorders particularly cancer, and identifying HLA compatible embryos suitable for recovering umbilical cord blood stem cells.

A mouse embryonic stem cell bank for inducible overexpression of human chromosome 21 genes

Background

Dosage imbalance is responsible for several genetic diseases, among which Down syndrome is caused by the trisomy of human chromosome 21.

Results

To elucidate the extent to which the dosage imbalance of specific human chromosome 21 genes perturb distinct molecular pathways, we developed the first mouse embryonic stem (ES) cell bank of human chromosome 21 genes. The human chromosome 21-mouse ES cell bank includes, in triplicate clones, 32 human chromosome 21 genes, which can be overexpressed in an inducible manner. Each clone was transcriptionally profiled in inducing versus non-inducing conditions. Analysis of the transcriptional response yielded results that were consistent with the perturbed gene's known function. Comparison between mouse ES cells containing the whole human chromosome 21 (trisomic mouse ES cells) and mouse ES cells overexpressing single human chromosome 21 genes allowed us to evaluate the contribution of single genes to the trisomic mouse ES cell transcriptome. In addition, for the clones overexpressing the Runx1 gene, we compared the transcriptome changes with the corresponding protein changes by mass spectroscopy analysis.

Conclusions

We determined that only a subset of genes produces a strong transcriptional response when overexpressed in mouse ES cells and that this effect can be predicted taking into account the basal gene expression level and the protein secondary structure. We showed that the human chromosome 21-mouse ES cell bank is an important resource, which may be instrumental towards a better understanding of Down syndrome and other human aneuploidy disorders.

Aneuploidies of chromosomes 1, 4, and 6 are not compatible with human embryos' implantation

OBJECTIVE

To verify whether chromosomes 1, 4, and 6 have a role in determining oocyte viability.

DESIGN

Retrospective study.

SETTING

Reproductive Medicine Unit, Società Italiana Studi Medicina della Riproduzione, Bologna, Italy.

PATIENT(S)

Eighty-five patients with a normal karyotype who had undergone an assisted conception cycle with chromosomal analysis of first polar bodies for chromosomes 13, 15, 16, 18, 21, and 22 (first panel). A clinical pregnancy was obtained in 43 patients, whereas 42 patients were not pregnant.

INTERVENTION(S)

After conclusion of clinical pregnancies to delivery or abortion, first polar bodies from 85 patients were reanalyzed for chromosomes 1, 4, and 6 (second panel).

MAIN OUTCOME MEASURE(S)

Aneuploidy frequency, clinical pregnancy outcome.

RESULT(S)

The aneuploidy rate contributed by chromosome 1, 4, and 6 to the oocytes that were normal for the first panel was significantly higher in the nonpregnant patients (28%) versus the pregnant patients (11%), whereas no difference resulted between term pregnancies (11%) and abortions (10%). This trend was also observed when studying the first polar bodies from the oocytes that originated the transferred embryos. The frequency of aneuploidy for chromosomes 1 and 4 was comparable with that of chromosomes 15, 16, 21, and 22.

CONCLUSION(S)

Aneuploidy of chromosomes 1, 4, and 6 seems to be related to failed implantation and not to spontaneous abortions.

Preimplantation genetic screening for abnormal number of chromosomes (aneuploidies) in in vitro fertilisation or intracytoplasmic sperm injection

BACKGROUND

In both in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI), selection of the most competent embryo(s) for transfer is generally based on morphological criteria. However, many women fail to achieve a pregnancy after transfer of good quality embryos. One of the presumed causes is that such morphologically normal embryos show an abnormal number of chromosomes (aneuploidies). In preimplantation genetic screening (PGS), embryos are analysed for aneuploidies and only embryos that are euploid for the chromosomes tested are transferred. This technique has been suggested and used to improve pregnancy rates for the following indications: (i) advanced maternal age, (ii) repeated IVF failure, (iii) repeated miscarriage and (iv) testicular sperm extraction (TESE)-ICSI. Although PGS is used more and more often, its effectiveness is still unclear.

OBJECTIVES

To assess the effectiveness of PGS in terms of live births in women undergoing IVF or ICSI treatment.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library Issue 1, 2005), MEDLINE (1966 to present) and EMBASE (1980 to present) (searched March 2005) and reference lists of articles. We also contacted authors for providing additional data when necessary.

SELECTION CRITERIA

Trials for all four suggested indications as mentioned above were sought. All relevant published randomised controlled trials were selected. They were eligible for inclusion if the comparison dealt with IVF/ICSI with PGS versus IVF/ICSI without PGS.

DATA COLLECTION AND ANALYSIS

Relevant data were extracted independently by two authors. All trials were screened and analysed according to predetermined quality criteria. Validity was assessed in terms of method of randomisation, completeness of follow-up, intention-to-treat analysis and presence or absence of blinding. The primary outcome measure was live birth rate per woman. Secondary outcome measures were the proportion of women reaching embryo transfer, mean number of embryos transferred per transfer, clinical pregnancy rate, multiple pregnancy rate, miscarriage rate, ongoing pregnancy rate, proportion of women reaching embryo transfer after cryopreservation and proportion of women whose child has a congenital malformation.

MAIN RESULTS

Two randomised controlled trials met our predetermined eligibility criteria. These trials used PGS for advanced maternal age. The primary outcome of live birth rate per woman was not significantly different in the PGS and control groups, though data were only available from one study. The live birth rate was 11% (21 out of 199) in the PGS group, versus 15% (29 out of 190) in the control group (OR 0.65; 95% CI 0.36 to 1.19). For a control group rate of 15%, these data suggest a live birth rate using PGS of between 4% and 17%. Ongoing pregnancy rate was provided in both studies. This was not significantly different with a combined odds ratio of 0.64 (95% CI 0.37 to 1.09). For a control group rate of 20%, this suggests an ongoing pregnancy rate using PGS of between 8% and 21%.

AUTHORS' CONCLUSIONS

To date there is insufficient data to determine whether PGS is an effective intervention in IVF/ICSI for improving live birth rates. Available data on PGS for advanced maternal age showed no difference in live birth rate and ongoing pregnancy rate. However, only two randomised trials were found, of which one included only 39 patients. For both studies comments on their methodological quality can be made. Therefore more properly conducted randomised controlled trials are needed. Until such trials have been performed PGS should not be used in routine patient care.