Should we perform oocyte accumulation to preserve fertility in women with Turner syndrome? A multicenter study and systematic review of the literature

STUDY QUESTION

Should we perform oocyte accumulation to preserve fertility in women with Turner syndrome (TS)?

SUMMARY ANSWER

The oocyte cryopreservation strategy is not well adapted for all TS women as their combination of high basal FSH with low basal AMH and low percentage of 46,XX cells in the karyotype significantly reduces the chances of freezing sufficient mature oocytes for fertility preservation.

WHAT IS KNOWN ALREADY

An oocyte cryopreservation strategy requiring numerous stimulation cycles is needed to preserve fertility in TS women, to compensate for the low ovarian response, the possible oocyte genetic alterations, the reduced endometrial receptivity, and the increased rate of miscarriage, observed in this specific population. The validation of reliable predictive biomarkers of ovarian response to hormonal stimulation in TS patients is necessary to help practitioners and patients choose the best-personalized fertility preservation strategy.

STUDY DESIGN, SIZE, DURATION

A retrospective bicentric study was performed from 1 January 2011 to 1 January 2023. Clinical and biological data from all TS women who have received from ovarian stimulation for fertility preservation were collected. A systematic review of the current literature on oocyte retrieval outcomes after ovarian stimulation in TS women was also performed (PROSPERO registration number: CRD42022362352).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 14 TS women who had undergone ovarian stimulation for fertility preservation were included, representing the largest cohort of TS patients published to date (n = 14 patients, 24 cycles). The systematic review of the literature identified 34 additional TS patients with 47 oocyte retrieval outcomes after ovarian stimulation in 14 publications (n = 48 patients, n = 71 cycles in total).

MAIN RESULTS AND THE ROLE OF CHANCE

The number of cryopreserved mature oocytes on the first cycle for TS patients was low (4.0 ± 3.7). Oocyte accumulation was systematically proposed to increase fertility potential and was accepted by 50% (7/14) of patients (2.4 ± 0.5 cycles), leading to an improved total number of 10.9 ± 7.2 cryopreserved mature oocytes per patient. In the group who refused the oocyte accumulation strategy, only one patient exceeded the threshold of 10 mature cryopreserved oocytes. In contrast, 57.1% (4/7) and 42.9% (3/7) of patients who have underwent the oocyte accumulation strategy reached the threshold of 10 and 15 mature cryopreserved oocytes, respectively (OR = 8 (0.6; 107.0), P = 0.12; OR= 11 (0.5; 282.1), P = 0.13). By analyzing all the data published to date and combining it with our data (n = 48 patients, n = 71 cycles), low basal FSH and high AMH concentrations as well as a higher percentage of 46,XX cells in the karyotype were significantly associated with a higher number of cryopreserved oocytes after the first cycle. Moreover, the combination of low basal FSH concentration (<5.9 IU/l), high AMH concentration (>1.13 ng/ml), and the presence of 46,XX cells (>1%) was significantly predictive of obtaining at least six cryopreserved oocytes in the first cycle, representing objective criteria for identifying patients with real chances of preserving an adequate fertility potential by oocyte cryopreservation.

LIMITATIONS, REASONS FOR CAUTION

Our results should be analyzed with caution, as the optimal oocyte number needed for successful live birth in TS patients is still unknown due to the low number of reports their oocyte use in the literature to date.

WIDER IMPLICATIONS OF THE FINDINGS

TS patients should benefit from relevant clinical evaluation, genetic counseling and psychological support to make an informed choice regarding their fertility preservation technique, as numerous stimulation cycles would be necessary to preserve a high number of oocytes.

STUDY FUNDING/COMPETING INTEREST(S)

This research received no external funding. The authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

[Are gestational weight gain guidelines for obese women still appropriate?]

Guidelines for adequate gestational weight gain were proposed in 2009 by the Institute of Medicine. In case of a BMI>30kg/m², the recommended gestational weight gain should be between 5 and 9kg. However, these recommendations do not distinguish between different grades of obesity. Recent data suggest that the IOM recommendations are not restrictive enough for obese pregnant women and should be adapted to the grade of obesity.

[What issues, changes and adaptations for French ART centers in the context of the new bioethics law?]

OBJECTIVE

This review intends to introduce the changes of the new Bioethics law in the reproductive field and its application in French ART centers.

MATERIAL AND METHODS

The review details the main provisions of the Bioethics Law of August 2nd 2021 as well as the three decrees published since: the first one on September 29th 2021, which specifies in particular the age conditions to benefit from ART and self-preservation of one's gametes; another decree on December 31st, 2021, to set the terms and conditions for gamete self-preservation activities for non-medical reasons and the last decree on April 14th 2022, relating to the allocation of donated gametes and embryo donation.

RESULTS

Since the law of August 2nd, 2021, access conditions to assisted reproductive technology (ART) have evolved in France. Previously based on pathological infertility or the risk of transmission of a serious disease, ART is now intended to respond to the parental project of a couple formed by a man and a woman, two women or an unmarried woman. With the widening of access conditions, the use of gamete donation will likely increase. The upcoming raise of children born from gamete donation has led the legislator to question their right to access their origin. From September 1st 2022, adults born from gamete donation will be able to request a special administrative authority in order to access the donor's non identifying data (age, physical characteristics, family and professional situation, motivation for the donation…) and/or the donor's identity. Moreover, the new bioethics law opens up the possibility of autologous gamete cryopreservation without medical reasons, under specific age conditions, in order to carry out an assisted reproduction technique later. If gametes are not used, autologous gamete preservation could also allow an increase in gamete donation. However, the modification of gamete donation conditions could suggest a short term decrease in donors' number. Finally, the new bioethics law further opens up research on human embryos and embryonic stem cells.

CONCLUSION

The arrangements introduced by the Bioethics Law promulgated on August 2nd, 2021 represent a major revolution in the field of Reproductive Medicine and are expected to transform the practices of reproductive biology centers and CECOS in France.

[HLA-C KIR interactions and placental defects: Implications in ART pregnancy issues]

OBJECTIVE

The aim of this review is to update data concerning the impact of HLA-C KIR system on placental disorders and assess the involvement on ART clinical outcomes.

METHOD

Ensuring the maintenance of human pregnancy requires the set up of immunological tolerance to prevent foetus rejection. This phenomenon involves different actors of the immune system: among them, uterine NK cells (uNK) hold specific KIR (killer-cell immunoglobulin-like) receptors linking to HLA molecules on the surface of trophoblastic cells at implantation. Many studies provided evidence that the specific interaction between maternal KIR and foetal HLA-C could influence the process of placentation; according to the KIR haplotype and the type of HLA-C, the interaction could be detrimental for placental function. We reviewed the latest data available regarding HLA-C KIR interactions and ART outcomes.

RESULTS

The available results highlight a significant increase of preeclampsia risk and recurrent miscarriages when the maternal inhibitory haplotype KIR AA is present, this risk is all the more enhanced when the interaction occurs with foetal HLA-C2. Recent data suggest the consequences of this detrimental interaction in case of DET (double embryo transfer) or use of donor's oocytes in ART practice. On the other hand, maternal KIR AB or BB haplotypes haven't been related to an additional obstetrical risk, as well as the foetal HLA-C1 homozygous allotype.

CONCLUSION

Despite the existence of many confoundings in current literature on the subject, interaction between maternal KIR and foetal HLA-C represent a promising target lead to broaden the spectrum of placental defects etiologies, especially in the reproductive health area.

P-219 Does artificial shrinkage prior to fresh blastocyst transfer improve ongoing pregnancy rate? A prospective double blind randomized controlled trial

Study question

Does artificial shrinkage (AS) of blastocoelic cavity (BC) prior to fresh elective single blastocyst transfer (SBET) increase ongoing pregnancy rate?

Summary answer

Ongoing pregnancy rates were similar with or without AS of blastocoelic cavity. AS does not seem to provide benefit before fresh blastocyst transfer.

What is known already

AS of the vitrified blastocysts enhances success rate in frozen embryo transfer cycles.

In vitro cultured embryos suffer changes in temperature, pH and osmotic pressure. Moreover, manipulations such as pipetting, fertilization, microscopic observations and changes of dishes can induce oxidative stress and apoptosis. The presence of cell free DNA (cfDNA) in blastocyst fluids could be the consequence of its release from dead cells. The quantity of cfDNA in blastocyst fluids could possibly be related to the rate of cell death. It is thus interesting to estimate whether AS of BC could improve the implantation rate in cycles with fresh blastocyst transfer.

Study design, size, duration

Prospective, randomized, double blind controlled study. From May 20th 2018 to June 30th 2021, 150 couples elected for fresh SBET were included in the study and were randomly selected as “AS +” group (n = 100), where AS of blastocoel was performed by laser pulse before fresh blastocyst transfer, and “AS -” group (n = 50), where fresh blastocysts were transferred without any additional intervention.

Participants/materials, setting, methods

On day 5 after fertilization, one blastocyst with a grade of expansion B3, B4, B5 or B6 and type A or B quality trophectoderm (Gardner and Schoolcraft classification, 1999) was selected for transfer. After replacement, the droplet that contained the embryo from day 3 was collected for cfDNA level quantification.

Ongoing pregnancy rate was determined by the visualization of a gestational sac with a foetal heartbeat 6 weeks later and cfDNA was assessed by ALU-qPCR.

Main results and the role of chance

The two groups were similar for age, BMI, infertility duration and cause, stimulation characteristics and embryological parameters. The global ongoing pregnancy rate per transfer after SBET was 49.7 %. The pregnancy rate in the AS + group was slightly higher than in the control group but not significantly (respectively 50.00 % and 48,9 %, p = 0,91).

cfDNA median value in the AS+ group was comparable to the control group (0.493 (0.219; 0.915) mg/ml and 0.595 (0.271; 1.129) mg/ml respectively (p = 0.45)). No link was found between cfDNA rate and clinical pregnancy rate.

Limitations, reasons for caution

Patients included in the study are still followed to evaluate the impact of AS on live birth rate, wastage rate, obstetrical and neonatal complications. cfDNA rate was evaluated in spent culture media and not by blastocentesis, which could provide a more accurate quantification.

Wider implications of the findings

To our knowledge, this is the first prospective randomized controlled study assessing the benefit of AS of BC before fresh blastocyst transfer. The inclusion of live birth rate is crucial to ascertain the interest of this technique and more studies are needed to improve the use of cfDNA in routine.

Trial registration number

NCT02988544

P-553 Response to controlled ovarian stimulation and preimplantation genetic testing for molecular disease (PGT-M) outcomes for Myotonic dystrophy type I (DM1) : A French multicentric study

Study question

Does ovarian response to controlled ovarian hyperstimulation (COH) is altered in female affected by DM1 ?

Summary answer

Ovarian response to COH is not altered in female affected by DM1 as compared to partners of affected males

What is known already

Myotonic dystrophy type 1 is the most common adult muscular dystrophy caused by a CTG trinucleotide repeat expansion which may expand across generation. As this pathology presents an autosomal dominant inheritance, PGT may be an option to achieve a pregnancy with healthy baby. There are conflicting reports about response to COH for affected female. Moreover, few data are available concerning the chance to have a healthy baby after PGT for couple with one member affected by DM1

Study design, size, duration

The present study is a retrospective observational study carried out from January 2006 through January 2020. This multicentric study was conducted in all the five centers performing PGT-M in France.

Participants/materials, setting, methods

A total of 229 couples started at least one COH cycle for the PGT procedure. The patient carrying the mutation was the female for 178 couples and the male for the 51 others. Overall, 648 COH cycles started and 560 oocytes retrieval for subsequent PGT were performed (430 for affected female and 130 for affected male). Parameters of ovarian response and PGT outcomes were compared according to the member affected by DM1.

Main results and the role of chance

Age and BMI at the first COH cycle were not significantly different between both group but female carried mutation presented lower AMH level than partner of affected male. The starting and total doses of gonadotrophin were significantly higher for mutated females. The number of retrieved and mature oocytes per cycle were not statistically different (12 [8–16] versus 11 [8–16] retrieved oocytes, p = 0.63 and 9 [6–13] versus 9 [6-13] mature oocytes, p = 0.73, respectively). In both group, more than 70% of oocyte retrieval led to embryo biopsy.

The proportion of started cycle allowing the obtention of at least one healthy embryo was significantly lower when the female was affected with DM1 (58.6% vs 70.4%, p = 0.012). In the female affected group, 49.7% of the cycles with oocytes retrieval lead to a fresh embryo transfer and a subsequent live birth rate per transfer of 21.4%. These results were not statistically different from the couple with affected male (58.5% of cycles with fresh embryo transfer (p = 0.08) and 23.6% live birth rate per transfer).

Overall, after fresh or frozen embryo transfer, 30.8% of females with DM1and 41.2% of parter of affected males had at least one live birth from PGT.

Limitations, reasons for caution

This a retrospective study included patients who were selected ovarian reserve parameters before PGT process. Moreover, the large time of inclusion may influence our conclusion.

Wider implications of the findings

Information provided herein extends knowledge about the current state of COH for DM1 affected female. Moreover, PGT results presented here allow to provide patients with proposer counseling before starting PGT process.

Trial registration number

CEROG-2020-GYN-0603

P–576 Preimplantation genetic testing for consanguineous couple carrying an identical reciprocal translocation: clinical, ethical considerations and quandaries

Study question

Which ethical and clinical aspects should be considered for preimplantation genetic testing PGT-SR strategy management for a consanguineous couple carrying the same reciprocal translocation?

Summary answer

PGT-SR management required specific probe designs to distinguish chromosomal patterns of balanced embryos, leading to complex transfer choices that required an adapted genetic counseling.

What is known already

Reciprocal translocation is a classic case in PGT-SR management, since all balanced embryos are transferable without distinguish between normal and balanced embryos. In accordance with the several recommendations, professionals calculated the reproductive risk related to the abnormalities and established an appropriate genetic counseling. However, an extreme case, such as the same reciprocal translocation carried by both members of a couple complicates PGT-SR management at all levels. Mainly, the genetics counseling around balanced embryo transfers. To date, only one study has reported a similar case, however, genetic counseling and the choice of embryos to be transferred have been poorly documented

Study design, size, duration

This study reports an extremely rare case of a couple (26-year-old woman and 29-year-old man) who was referred to our PGT center of the Montpellier University Hospital after 4 spontaneous miscarriages. The couple, first degree cousins in whom both partners are carrying the same reciprocal translocation 46,XX/XY,t(3;18) t(q26.1;q12.1). The patients were informed of the investigations and gave their consent before participation in the study.

Participants/materials, setting, methods

Peripheral blood of each member was investigated by FISH to caracterize chromosomal breakpoints. Secondly, a theoretical estimation of different segregation products to find a normal or balanced embryos were performed considering the extreme complexity of the case. Finally, an adapted PGT-SR probe strategy was conceived and proposed to a couple. Choices of balanced embryos to transfer were detailed to ensure that the patient is aware of risks and potential benefits.

Main results and the role of chance

In this particular case where both members of the couple are carrying the same reciprocal translocation, the chance of finding a normal or balanced embryo was further lowered 2% (4/196). It is estimated that the couple would produce 1 normal embryo and 15 balanced embryos. Diagnostic was possible on 16 biopsied embryos on day 3. Probe signal interpretations revealed four balanced embryos. Two embryos were proposed for a transferred on day 4. These balanced embryos had a different probe patterns, the first balanced embryo was normal and the second balanced embryo resulting from an adjacent–1 segregation mode presented an uniparental disomy (UPD).

Limitations, reasons for caution

ESHRE recommendations were established for common chromosomal rearrangements. In specific cases, limitations are strongly related to the complexity of the human genome. In this study, the choice of the embryos to be transferred depended entirely to our knowledge of phenotypic consequences of a homozygous gene alterations involved in chromosomal breakpoints.

Wider implications of the findings: Professionals were confronted with requests to transfer balanced embryos with a partial/complete UPD or a balanced double translocation homozygote to improve the transfer rate from 3/196 of balanced combinations to 16/196. Dilemma between risks and benefits were considered for counseling to ensure an informed decision-making by patients.

Trial registration number

NA

[Oncofertility and breast cancer at Montpellier University Hospital: Retrospective analysis of patients management since 2011]

OBJECTIVE

Five to 7% of breast cancers affect women under 40 years old. The survival of these patients has been improved thanks to therapeutic advances, often to the detriment of their fertility. The objective of this study is to evaluate the activity of oncofertility and the future of young women with breast cancer managed at the Montpellier University Hospital.

METHODS

This is a retrospective study including women aged from 18 to 43 years-old diagnosed with breast cancer and referred in oncofertility consultation at the Montpellier University Hospital between July 2011 and December 2018.

RESULTS

190 patients were eligible, three refused to participate to the study, hence 187 patients were included. We estimate that only 33% of young breast cancer patients potentially eligible for fertility preservation (FP) benefited from an oncofertility consultation in our region. Of these 187 patients, 58 (31%) underwent ovarian stimulation for oocyte or embryo vitrification. They were significantly younger: 32.9 vs 34.6 years old (P=0.01) and had fewer invaded lymph nodes. A total of 66 cycles were achieved and 11.4 oocytes or 3 embryos were vitrified per patient. The reuse rate was 3.6% with 91% of post cancer pregnancies being spontaneous.

CONCLUSION

The oncofertility care network seems effective at the regional level. Enhancing health professionals' awareness and creating a regional register could improve our long-term follow-up.

[Natural cycle for frozen-thawed embryo transfer: Spontaneous ovulation or triggering by HCG]

OBJECTIVE

To compare frozen-thawed embryo transfer (FET) outcomes in natural cycles according to ovulation induction: spontaneous versus recombinant human chorionic gonadotrophin (r-hCG) triggering.

METHODS

This retrospective study included all patients monitored for natural cycle FET during one year. When serial monitoring were performed until spontaneous LH rise, patients were included in group A (n=38) whereas those receiving r-hCG for ovulation triggering formed group B (n=43). All embryos had been cryopreserved by a vitrification method following a previous IVF cycle. No luteal phase support had been given. We compared outcomes between the 2 groups.

RESULTS

After checking groups comparability, we didn't find significant difference for the implantation rate, clinical pregnancy rate and live birth (31% vs 45%, 32% vs 51% et 21% vs 32%, respectively for group A and B). The number of monitoring was significantly lower in group B (1,9±0,8 versus 2,5±1, P=0,006).

DISCUSSION

Although no consensus has been yet established, natural cycle seems indicated for normo-ovulating patients but the question of ovulation induction is still debated. In our study, triggering ovulation by r-hCG, respecting strict criteria, seems provide good results while reducing both protocol's constraints and cost.

Preimplantation genetic diagnosis for cystic fibrosis: the Montpellier center's 10-year experience

This study provides an overview of 10 years of experience of preimplantation genetic diagnosis (PGD) for cystic fibrosis (CF) in our center. Owing to the high allelic heterogeneity of CF transmembrane conductance regulator (CFTR) mutations in south of France, we have set up a powerful universal test based on haplotyping eight short tandem repeats (STR) markers together with the major mutation p.Phe508del. Of 142 couples requesting PGD for CF, 76 have been so far enrolled in the genetic work-up, and 53 had 114 PGD cycles performed. Twenty-nine cycles were canceled upon in vitro fertilization (IVF) treatment because of hyper- or hypostimulation. Of the remaining 85 cycles, a total of 493 embryos were biopsied and a genetic diagnosis was obtained in 463 (93.9%), of which 262 (without or with a single CF-causing mutation) were transferable. Twenty-eight clinical pregnancies were established, yielding a pregnancy rate per transfer of 30.8% in the group of seven couples with one member affected with CF, and 38.3% in the group of couples whose both members are carriers of a CF-causing mutation [including six couples with congenital bilateral absence of the vas deferens (CBAVD)]. So far, 25 children were born free of CF and no misdiagnosis was recorded. Our test is applicable to 98% of couples at risk of transmitting CF.

Effects of cigarette smoking on reproduction

BACKGROUND Cigarette smoking is associated with lower fecundity rates, adverse reproductive outcomes and a higher risk of IVF failures. Over the last few decades, prevalence of smoking among women of reproductive age has increased. This review focuses on current knowledge of the potential effects of smoke toxicants on all reproductive stages and the consequences of smoke exposure on reproductive functions. METHODS We conducted a systematic review of the scientific literature on the impact of cigarette smoking and smoke constituents on the different stages of reproductive function, including epidemiological, clinical and experimental studies. We attempted to create hypotheses and find explanations for the deleterious effects of cigarette smoke observed in experimental studies. RESULTS Cigarette smoke contains several thousand components (e.g. nicotine, polycyclic aromatic hydrocarbons and cadmium) with diverse effects. Each stage of reproductive function, folliculogenesis, steroidogenesis, embryo transport, endometrial receptivity, endometrial angiogenesis, uterine blood flow and uterine myometrium is a target for cigarette smoke components. The effects of cigarette smoke are dose-dependent and are influenced by the presence of other toxic substances and hormonal status. Individual sensitivity, dose, time and type of exposure also play a role in the impact of smoke constituents on human fertility. CONCLUSIONS All stages of reproductive functions are targets of cigarette smoke toxicants. Further studies are necessary to better understand the deleterious effects of cigarette smoke compounds on the reproductive system in order to improve health care, help to reduce cigarette smoking and provide a better knowledge of the molecular mechanisms involved in reproductive toxicology.

Predictive value of sperm-FISH analysis on the outcome of preimplantation genetic diagnosis (PGD) for a pericentric inversion inv5(p15.3q11.2) carrier

BACKGROUND

Pericentric inversions (PIs) are structural chromosomal abnormalities, potentially associated with infertility or multiple miscarriages. More rarely, at meiosis, odd numbers of genetic recombinations within the inversion loop produce recombinant gametes which may lead to aneusomy of recombination in the offspring.

METHODS

We report a FISH segregation analysis of an inv5(p15.3q11.2) carrier, both in sperm and blastomeres. In sperm, we directly evaluated the proportion of recombinant gametes and compared the results with chromosomal abnormalities found in blastomeres collected from embryos obtained following a preimplantation genetic diagnosis (PGD) procedure.

RESULTS

A total of 7006 sperm nuclei were analyzed. The size of the inverted segment represented 27% of the total length of chromosome 5. The frequencies of balanced chromosomes (normal or inverted), recombinant chromosomes and unbalanced combinations were 97.1, 0.17 and 2.73%, respectively. Of six embryos, PGD FISH analysis revealed that one was a balanced embryo, whereas five were unbalanced and there were no recombinants.

CONCLUSIONS

This study demonstrated the value of sperm-FISH analysis in providing reproductive genetic counseling for PI carriers. Our study also highlights the clinical relevance of performing PGD instead of prenatal diagnosis.

The cell cycle control protein cdc25C is present, and phosphorylated on serine 214 in the transition from germinal vesicle to metaphase II in human oocyte meiosis

Cdc25C is a dual specificity phosphatase essential for dephosphorylation and activation of cyclin-dependent kinase 1 (cdk1), a prerequisite step for mitosis in all eucaryotes. Cdc25C activation requires phosphorylation on at least six sites including serine 214 (S214) which is essential for metaphase/anaphase transit. Here, we have investigated S214 phosphorylation during human meiosis with the objectives of determining if this mitotic phosphatase cdc25C participates in final meiotic divisions in human oocytes. One hundred forty-eight human oocytes from controlled ovarian stimulation protocols were stained for immunofluorescence: 33 germinal vesicle (GV), 37 metaphase stage I (MI), and 78 unfertilized metaphase stage II (MII). Results were stage dependent, identical, independent of infertility type, or stimulation protocol. During GV stages, phospho-cdc25C is localized at the oocyte periphery. During early meiosis I (MI), phosphorylated cdc25C is no longer detected until onset of meiosis I. Here, phospho-cdc25C localizes on interstitial microtubules and at the cell periphery corresponding to the point of polar body expulsion. As the first polar body reaches the periphery, phosphorylated cdc25C is localized at the junction corresponding to the mid body position. On polar body expulsion, the interior signal for phospho-cdc25C is lost, but remains clearly visible in the extruded polar body. In atresic or damaged oocytes, the polar body no longer stains for phospho-cdc25C. Human cdc25C is both present and phosphorylated during meiosis I and localizes in a fashion similar to that seen during human mitotic divisions implying that the involvement of cdc25C is conserved and functional in meiotic cells.

Le cycle naturel en fécondation in vitro chez les mauvaises répondeuses

Since the beginning of IVF, natural cycle In Vitro Fertilization (NC-IVF) has been largely replaced by IVF with ovarian stimulation. However, natural cycle IVF has several advantages: low cost, no risk of ovarian hyper stimulation syndrome, very low risk of multiple pregnancy. Nevertheless, natural cycle IVF is less effective with a high risk of cancellation due to premature rise of LH, and an increased risk of failed oocyte retrieval. Using GnRH antagonists in a modified natural cycle decreases the occurrence of a premature LH rise. In the context of a poor responder patient, natural IVF could theoretically yield a better quality oocyte coming from a naturally selected follicle and allow a transfer on an endometrium whose receptivity has not been distorted by controlled ovarian stimulation. However, the real place for it has yet to be defined as we lack published data. Only one randomised controlled study in poor responders showed a similar pregnancy rate to a standard protocol representing a cost-effective alternative. Available retrospective data seem to show the same trend especially in the sub group of younger patients (below 38). Natural cycle IVF is a low-risk, low-cost procedure whose interesting results should be further confirmed by large scale prospective studies.

Effect of maternal age on the frequency of cytogenetic abnormalities in human oocytes

The cytogenetic investigation of human oocytes was initiated in the Sixties, and for the last four decades, this field of research has never stopped progressing as new technologies appear. Numerous karyotyping studies and molecular cytogenetic studies have been reported to date, providing a large body of data on the incidence and the distribution of chromosomal abnormalities in human female gametes, but also displaying a great variability in results, which may be essentially attributable to the technical limitations of these in situ methods when applied to human oocytes. Essentially, the most relevant analyses have led to the estimate that 15-20% of human oocytes display chromosome abnormalities, and they have emphasized the implication of both whole chromosome nondisjunction and chromatid separation in the occurrence of aneuploidy in human oocytes. The effect of advanced maternal age on the incidence of aneuploidies has also been investigated in human oocytes. Most previous studies have failed to confirm any relationship between maternal age and aneuploidy frequency in human oocytes, whereas the more recent reports based on large samples of oocytes or polar bodies have provided evidence for a direct correlation between increased aneuploidy frequency and advanced maternal age, and have clarified the contribution of the various types of malsegregation in the maternal age-dependent aneuploidies.

Cytogénétique des ovocytes humains : 40 ans de progrès

Chromosomal abnormalities account for the majority of pre- and post- implantation embryo wastage in humans. Most of these abnormalities result from maternal meiotic errors, which preferentially occur during the first meiotic division. Consequently, the cytogenetic analysis of human oocytes has then been considered as a highly valuable source of data for the investigation of both the occurrence and the origin of chromosomal abnormalities in human. During the last 4 decades, the cytogenetic analysis of human oocytes has never stopped progressing, according to the advents of new technologies. Both karyotyping and molecular cytogenetic studies have been reported to date, providing a large body of data on the incidence and the distribution of chromosomal abnormalities in human female gametes. However, these studies display a great variability in results, which may be essentially attributable to the limitations of these techniques when applied to human oocytes. The most relevant analysis have led to the estimate that 15-20% of human oocytes present chromosome abnormalities, and they have emphasized the implication of both whole chromosome non-disjunction and chromatid separation in the occurrence of aneuploidy in human oocytes. The effect of advanced maternal age on the incidence of aneuploidy in human oocytes has also been clearly evidenced by recent reports based on large sample of oocytes or polar bodies.

Sperm segregation analysis of a (13;22) Robertsonian translocation carrier by FISH: a comparison of locus-specific probe and whole chromosome painting

BACKGROUND

The t(13;22) Robertsonian translocation constitutes a rare form of rearrangement between acrocentric human chromosomes. Most of the meiotic segregation studies of human Robertsonian translocations have been performed on common t(13;14) and t(14;21) translocations. Analysis of the chromosomal constitution in sperm of Robertsonian translocation carriers is of great interest for assessing the risk of unbalanced forms and adapting genetic counselling. In the present study, we present the first meiotic segregation study of a t(13;22) Robertsonian translocation in human sperm.

METHODS

A total of 11 787 sperm nuclei were scored using two distinct FISH labelling techniques, i.e. the locus-specific probes (LSI) method and the whole chromosome painting (WCP) technique.

RESULTS

The frequency of normal or balanced sperm resulting from alternate meiotic segregation was 86%. Incidences of unbalanced complements resulting from adjacent segregation modes were 12.79% and 14.36% in LSI and WCP assays, respectively. No significant excess of nullisomy or disomy for the affected chromosomes was observed.

CONCLUSIONS

Similar results in segregation were obtained with the two techniques, demonstrating the efficiency of the two strategies for the direct segregation analysis of Roberstsonian translocations. The results obtained indicated a moderate meiotic production of imbalance. This study shows that the rare Robertsonian translocation (13;22) displays a similar distribution of balanced and unbalanced sperm patterns as the common Robertsonian translocations previously studied. This suggests that the behaviour of acrocentric chromosomes was similar in all cases of centric fusion.

The chromosomal analysis of human oocytes. An overview of established procedures

The cytogenetic survey of mature human oocytes has been and remains a subject of great interest because of the prevalence of aneuploidy of maternal origin in abnormal human conceptuses, and the lack of understanding about the non-disjunction processes in human meiosis. The first attempts to analyse the chromosomal content of human female gametes were made in the early 1970s, and led to limited data because of the paucity of materials and the inadequacy of the procedure used. The years to follow brought a resurgence of interest in this field, because of the development of human IVF techniques which made oocytes unfertilized in vitro available for cytogenetic analysis. Numerous studies have since been performed. However, the difficulties in obtaining good chromosome preparations and of performing accurate chromosome identification have reduced the viability of these studies, resulting in large variations in the reported incidences of chromosomal abnormalities. The further introduction of new procedures for oocyte fixation and the screening of large oocyte samples have allowed more reliable data to be obtained and to identify premature chromatid separation as a major mechanism in aneuploidy occurrence. The last decade has been privileged to witness the adaptation of molecular cytogenetic techniques to human oocytes, and thus various powerful procedures have been tried not only on female gametes, but also on polar bodies, involving sequential and multicolour fluorescent in situ hybridization (FISH) labelling, comparative genomic hybridization (CGH), spectral karyotyping and alternative methods such as primed in situ labelling (PRINS) and peptide nucleic acid (PNA) techniques. A large body of data has been obtained, but these studies also display a great variability in the frequency of abnormalities, which may be essentially attributable to the technical limitations of these in situ methods when applied to human oocytes. However, molecular cytogenetic approaches have also evidenced the co-existence of both whole chromosome non-disjunction and chromatid separation in maternal aneuploidy. In addition, the extension of these techniques to oocyte polar body materials has provided additional data on the mechanism of meiotic malsegregation. Improvements of some of these techniques have already been reported. The further development of new approaches for the in situ analysis of human meiosis will increase the impact of cytogenetic investigation of human oocytes in the understanding of aneuploidy processes in humans.

Sequential multiple probe fluorescence in-situ hybridization analysis of human oocytes and polar bodies by combining centromeric labelling and whole chromosome painting

The incidence of chromosomal aneuploidy was analysed in 104 unfertilized human oocytes and 56 first polar bodies using a double-label fluorescence in-situ hybridization (FISH) procedure. Combinations of centromeric (or locus-specific) DNA probes and whole chromosome painting probes for chromosomes 9, 13, 16, 18, 21 and X were applied on oocyte preparations, in a sequential FISH protocol. This combined approach allowed a precise in-situ identification of both chromosomes and free chromatids, and consequently a reliable analysis of chromosomal segregation errors. Of the 104 analysed oocytes, 84 (80.7%) displayed a normal chromosome constitution. Three cases of chromosome non-disjunction (2.8%) were found, whereas seven oocytes (6.7%) presented extra single chromatids. In addition, 12 oocytes (11.5%) showed balanced pre-division of one pair of sister chromatids. Although this phenomenon was not classified as aneuploidy, it could lead to aneuploidy at anaphase II. Abnormalities were observed in all the targetted chromosomes. The present data confirm that both whole chromosome non-disjunction and premature chromatid separation constitute the two major mechanisms of aneuploidy in human female meiosis.

Specific detection of deleted and non-deleted dystrophin exons together with gender assignment in preimplantation genetic diagnosis of Duchenne muscular dystrophy

We have developed a preimplantation genetic diagnosis (PGD) strategy for Duchenne muscular dystrophy (DMD) allowing the simultaneous amplification of four exons (6, 8, 28 and 32) of the dystrophin gene together with ZFX/ZFY genes for gender determination. Preliminary experiments were carried out on 215 single lymphocytes from male and female individuals. Amplification rates ranged from 90.2% for exon 6 to 96.7% for exons 8 and 32. At least four of the five sequences were successfully amplified in 95.8% of single cells, and sexing was possible in 98.5%. This 5-plex assay was found to be robust enough to be used in a PGD clinical procedure and was therefore applied to a family whose female partner was a heterozygous carrier of a large deletion extending from exon 21 to exon 34 of the dystrophin gene. We have thus analysed two exons located in the deleted region of the gene, two non-deleted exons used as intrasample controls, and ZFX/ZFY genes. Cleavage stage embryo biopsy followed by PCR resulted in transfer of three unaffected embryos. The advantage of the present approach is to identify and subsequently transfer unaffected male embryos in addition to female embryos, and is now applicable to all families displaying a deletion involving at least one of these exons.

First preimplantation genetic diagnosis of hereditary retinoblastoma using informative microsatellite markers

Retinoblastoma is a malignant intra-ocular tumour of developing retina initiated by inactivation of both alleles of the retinoblastoma susceptibility (RB1) gene. This paper reports the first clinical experience of preimplantation genetic diagnosis (PGD) for hereditary retinoblastoma using two highly polymorphic microsatellite markers RB1.20 and D13S284, located within and close to the RB1 gene respectively. Duplex PCRs were tested on more than 300 single lymphocytes from heterozygous individuals at both loci, in order to test the accuracy and reliability of the single-cell protocol. This procedure requires a nested PCR and the analysis of fluorescently labelled PCR products on an automatic DNA sequencer. Amplification efficiency and allele drop-out rates ranged from 96.7 to 98.4%, and 3.7 to 5.4% respectively. This test was found to be accurate and reliable enough to be applied to the study of human blastomeres. Subsequently, this approach was used in a PGD treatment cycle for a couple who already had a child affected with hereditary retinoblastoma and found to be informative for both microsatellite markers.

Salpingectomy for repeated embryo nonimplantation after in vitro fertilization in patients with severe tubal factor infertility

PURPOSE

To evaluate the impact of salpingectomy on the rates of embryo implantation and pregnancy in patients with severe, irreversible tubal factor sterility.

METHODS

A retrospective study of patients with repeated failure of in vitro fertilization due to nonimplantation of the embryo. Seventy-two patients with severe and irreversible tubal factor sterility were selected following repeated failure of in vitro fertilization (IVF) due to assumed nonimplantation of the embryo: 35 underwent a salpingectomy before continuing IVF cycles and 37 continued IVF cycles without salpingectomy.

RESULTS

After the first IVF cycle consecutive to diagnosis of embryo nonimplantation, the implantation rate was 10.2% in the salpingectomy group and 6.1% in the group without the procedure (P = 0.5). After all IVF cycles, the rate was, respectively, 6.9% and 4.5% (P = 0.2). Salpingectomy improved the pregnancy rate (PR) per transfer (23.5% vs. 9.9%; P = 0.01). The curves of the cumulative probability of becoming pregnant show that salpingectomy resulted in pregnancy more rapidly.

CONCLUSIONS

Salpingectomy improves the PR per transfer in patients with severe and irreversible tubal factor sterility who have experienced repeated failure of IVF due to embryo nonimplantation. This procedure also reduces the number of IVF attempts needed to obtain pregnancy.