FormalPara What does this study add to the clinical work

In this study we found that serum progesterone on trigger day did not affect embryo ploidy or embryo quality parameters in donated egg cycles. In an era marked by cycles with freeze all, PGT-A and FET, in which the percentage of IVF treatments using donated eggs only grows, our data should be of important interest to the Human Reproduction community worldwide and in relevance for planning and improving egg donation cycles, with benefits for the infertile couple.

Introduction

Chromosome aneuploidy in human embryos, whether they are generated by natural conception or by assisted reproductive technologies (ART), is the main cause for failed implantation, pregnancy loss and congenital birth defects [1]. The vast majority of aneuploidies are caused by errors in chromosomal/chromatid segregation during maternal meiosis and are known to be maternal age-related [2]. The incidence of aneuploidies increases from approximately 30% in patients younger than 35 years to 80% in women 42 years and older [3]. These chromosomal abnormalities can also occur after fertilization, during meiosis resumption and subsequent mitoses [4], leading to mosaicism in embryos. These errors can result in aneuploid embryos or embryos with chromosomal mosaicism.

Despite the high frequency of human aneuploidy in older women and its clinical importance [5], the mechanisms underlying aneuploidy are still poorly understood. Apart from maternal age, the exact cause of these numeric imbalances it is not known.

Over the years, many studies have tried to answer the question whether other factors involved in in vitro fertilization (IVF) treatments could interfere with the normal physiology of the oocyte maturation, fertilization process, subsequent embryonic development and, therefore, increase aneuploidy rates in embryos. Ovarian stimulation protocols [6, 7], fertilization method [8] and laboratory conditions [9], such as embryo culture media, pH, oxygen, osmolarity and temperature, have been proposed as possible candidates to increase meiotic errors. The documented variability in the frequency of aneuploid embryos between fertility centers [10] suggests that these IVF variables might contribute to the incidence of aneuploidy.

Since P4 plays a key role in the reproductive process and elevated P4 occurs in up to 46% of stimulated cycles [11], recently, the influence of high P4 values in IVF cycles and its possible detrimental effect on embryo ploidy have been investigated [12,13,14].

Studies have already demonstrated the presence of membrane receptors with high affinity for P4 in mammalian oocytes, including humans, and their ability to bind to P4 [15]. In recent years, compelling evidence has shown that the P4 receptor membrane component 1 (PGRMC1) is expressed in many cells of the mammalian reproductive system, where it exerts diverse functions [16]. In the ovary, PGRMC1 affects follicular growth by controlling cell viability and granulosa’s proliferation. PGRMC1 also appears to have a direct role in promoting the proper completion of oocyte maturation and in early embryonic development [16].

In animal models, it has been demonstrated that PGRMC1 may have an important role in oocyte maturation, more specifically related to the mechanism of chromosome segregation and polar body extrusion [16]. The mechanism by which PGRMC1 controls mitotic and meiotic cell division appears to involve an association with the cell spindle apparatus. According to recent analyzes and data, PGRMC1 participates in key mechanisms that control the progression of meiosis, such as spindle formation, stabilization of cytoskeletal elements, faithful separation of bivalent chromosomes, and cytokinesis, processes that are essential for proper maturation of the oocyte [16]. These findings suggest that alterations in the activity of the PGRMC1 could account in part for low oocyte development competence, reflecting at increased errors in chromosome segregation and, consequently, in aneuploid embryos.

Based on experimental evidence and clinical data, our hypothesis is that extra-physiological P4 levels in IVF ovarian stimulation could interfere with oocyte maturation via specific oocyte membrane receptors, leading to inadequate segregation of chromosomes during meiosis and, consequently, increasing embryo aneuploidy. This study aimed to explore if P4 levels on the day of the trigger affect the prevalence of aneuploidy in embryos generated from donated eggs in IVF cycles.

Material and methods

Study design

This is a retrospective single-center cohort study that analyzed 259 intracytoplasmic sperm injection (ICSI) cycles using frozen donated oocytes that underwent PGT-A at blastocyst stage performed between April/2013 and February/2019. Patients were divided in two groups according to P4 value on day of trigger: group A if P4 < 1.5 ng/mL and group B if P4 ≥ 1.5 ng/mL. A threshold P4 value of 1.5 ng/mL was chosen based on published literature [17]. Only euploid embryos were transferred to recipients. Primary outcome was embryo euploidy and aneuploidy rate. Secondary outcomes were number of blastocysts, number of top-quality embryos, number of euploid/aneuploid embryos and clinical pregnancy rate. Since it is already well documented that serum P4 on trigger is significantly correlated with the number of follicles and number of oocytes [13], in order to adjust the results of the studied outcomes, we calculated the P4/AFC index of the donors. Two new groups were created using the median of the P4/AFC index as a cut-off point: group 1 presented a P4/AFC index < 0.1 (n = 126 cycles) and group 2 presented a P4/AFC index ≥ 0.1 (n = 133 cycles).

Patient selection

Oocyte donors

Donors were women between 18 and 35 years of age, with regular menstrual cycles, body mass index (BMI) under 30 kg/m2, normal karyotype, with no gynecological or other health diseases and antral follicular count (AFC) ≥ 12. They also had no family history of hereditary or chromosomal diseases and were not exposed to radiation, hazardous chemical substances or intravenous drugs. All donors included in this study joined our oocyte program between April/2013 and February/2019. All of them underwent ovarian stimulation during this time interval.

Due to high ovarian reserve, a single donor, after ovarian stimulation, was able to donate their eggs to more than one recipient. Since in Brazil egg donation is anonymous and there is no financial compensation for donors, it is common for a donor to donate her eggs to more than one couple, especially considering the increasing number of cycles using donated eggs all around the world over the years.

Oocyte recipients

Oocyte recipients were admitted in our oocyte donation program due to advanced maternal age, premature ovarian failure or low response to previous stimulation. Recipients chose to perform preimplantation genetic testing (PGT-A) in oocyte donors’ cycles because of their own personal reasons; it was not due to medical recommendation. It is worth to mention that according to Brazilian law, with exception to sexual violence and/or maternal health risk, pregnancy interruption is forbidden by social/psychological reasons. Each recipient received a quantity of 8–12 eggs in order to optimize the chance of pregnancy and live birth rates [18].

Exclusion criteria

Cases with severe male infertility (< 5 million of fresh spermatozoa) were not included in the present study.

Laboratory procedures

Stimulation protocol

All oocyte donors received standard ovarian stimulation protocol with GnRH antagonist. Recombinant follicle-stimulating hormone (rFSH) or human menopausal gonadotropin (hMG) was administered starting on day 2–3 of the menstrual cycle. The dose of gonadotropin was individualized for each patient according to AFC and follicular development during stimulation. When a lead follicle reached 13 mm in diameter, the GnRH antagonist was initiated. The GnRH antagonist was administered daily until the day of trigger. Final oocyte maturation was induced when at least two lead follicles reached 20 mm in diameter with GnRH agonist. Thirty-five to thirty-six hours after trigger, the oocytes were collected via transvaginal ultrasound guidance. Mature oocytes (MII) were then cryopreserved.

Embryo biopsy

Post-thaw mature oocytes were fertilized using ICSI. At our center, incubation conditions are set at 37 °C; 6% CO2; 5% O2. Embryo development was evaluated until the day of biopsy. We used the morphologic criteria established by the Istanbul Consensus to classify the embryos. The scoring system for blastocysts was a combination of the stage of development and the grade of the inner cell mass and the trophectoderm [19].

Embryo biopsy was performed at blastocyst stage, on days 5 or 6 of development, using laser technology. Three to eight cells from the trophectoderm were collected to perform PGT-A. The samples were analyzed by array comparative hybridization technology (CGH) or next-generation sequencing (NGS). ACGH was the method used in our center in 2013, 2014 and 2015 and NGS was introduced in 2016. Embryos were classified as euploid (46, XX or 46, XY) or aneuploid (if they have an extra or missing chromosome). Mosaicism and other chromosome abnormalities were considered as aneuploid.

Embryo transfer

Frozen embryo transfer (FET) cycle preparation was performed with hormone replacement treatment. Only euploid embryos were transferred to recipients.

Progesterone measurement

Donor serum P4 was measured on trigger day using chemiluminescence immunoassay (Elecsys Progesterone III, Roche Diagnostics). The sensitivity of the assay was 0.03 μg/L. All donors underwent blood tests at Cerba laboratory to avoid bias.

Outcomes

The primary outcome was embryo euploidy and aneuploidy rate. Secondary outcomes were the number of blastocysts available for biopsy, number of top-quality embryos, number of euploid/aneuploid embryos and clinical pregnancy rate.

Statistical analysis

Statistical analysis was performed with SPSS version 17. Quantitative results are presented as mean and  standard deviation and frequencies, percentages for qualitative data. After the evaluation of the normal distribution or not of quantitative data, comparisons were performed with Student’s T test (parametric test for normal data) or the Mann–Whitney U test (non-parametric test for non-normal data). All rates are presented as mean values except for clinical pregnancy rate which is presented as n (%). For all calculations, a P value of < 0.05 was considered as statistically significant. According to statistical analysis, the minimum number of participants per group is 24. The sampling power of our study is 99.8%.

Ethics approval

This study was performed in line with the principles of the Declaration of Helsinki and approved by the Ethical Committee of Clinical Research at Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo  (CAAE number 40900820.5.0000.0068).

Results

A total of 259 ICSI PGT-A cycles with frozen donated oocytes were included in this study. Based on P4 value on the day of trigger, 75 cycles (29.0%) presented serum P4 < 1.5 ng/m (group A) and 184 cycles (71.0%) presented serum P4 ≥ 1.5 ng/mL (group B). Group A included 57 donors and 69 recipients and Group B included 115 donors and 163 recipients.

Donors’ cycles

Donors’ baseline characteristics and ovarian stimulation outcomes are summarized in Table 1. Donors’ age ranged from 18 to 34 years and was statistically similar between the two groups. Average donor age was 25.15 ± 3.59 years for group A and 24.46 ± 3.73 years for group B (P = 0.190). Group B had a higher AFC than Group A (22.95 ± 10.65 vs 19.60 ± 7.08, P = 0.030).

Table 1 Donors’ baseline characteristics and controlled ovarian stimulation parameters data comparisons between groups based on serum progesterone on the day of trigger
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It is already well documented that serum P4 levels on trigger during IVF cycles are attributed to an excessive number of follicles, each one producing a normal amount of P4 during follicular development [11]. In other words, the greater the number of follicles and oocytes, the higher are P4 levels. As a result, premature P4 elevation is a commonly observed phenomenon in donor’s cycles during controlled ovarian hyperstimulation due to the high ovarian reserve of donor patients [20]. In our study, since Group B presented a higher AFC, it included a greater number of cycles in its sample.

Regarding the ovarian stimulation cycle, total gonadotropin dosage (2777.83 ± 526.02 IU vs 2814.54 ± 538.78 IU, P = 0.736) and basal FSH (5.19 ± 1.51 IU/L vs 5.22 ± 1.47 IU/L, P = 0.303) were not different between groups A and B, respectively. Estradiol levels on the day of trigger (5255.00 ± 6405.77 pg/mL vs 5252.83 ± 4346.33 pg/mL, P = 0.034), number of retrieved eggs (33.96 ± 14.39 vs 28.01 ± 11.78, P = 0.001) and number of mature oocytes (24.84 ± 11.74 vs 21.12 ± 10.56, P = 0.008) were significantly higher in Group B (probably due to a higher AFC). There was no difference in the MII rate between the two groups (A: 0.75 ± 0.16 vs B: 0.73 ± 0.16, P = 0.071).

Recipients’ cycles

Average recipient age was 43.04 ± 4.47 years for group A and 42.27 ± 3.56 years for group B (P = 0.189). Both groups had similar BMI (23.94 ± 3.57 vs 23.52 ± 3.68 k/m2, P = 0.575). Outcomes of recipients’ cycles are presented in Table 2. There were no differences in the number of fertilized oocytes (A: 6.28 ± 1.45 vs B: 6.61 ± 1.59, P = 0.168) or fertilization rate (A: 0.83 ± 0.14 vs B: 0.82 ± 0.13, P = 0.854) between the two groups.

Table 2 Recipients’ cycle outcomes comparisons between groups based on serum P4 level on the day of trigger
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Regarding embryo development, number of blastocysts (3.60 ± 1.52 vs 3.68 ± 1.52, P = 0.667), number of biopsied blastocyst (3.15 ± 1.33 vs 3.06 ± 1.29, P = 0.699) and number of top-quality embryos (2.27 ± 1.59 vs 2.28 ± 1.43, P = 0.802) were found not to be significantly different between groups A and B, respectively. Seminal parameters were similar between the two groups.

A total of 155 blastocysts (16.35%) were analyzed by CGH and 793 blastocysts (77.95%) were analyzed by NGS. Numbers of euploid embryos (A: 1.92 ± 1.25 vs B: 1.92 ± 1.13, P = 0.954), euploid embryo rate (A: 0.31 ± 0.20 vs B: 0.30 ± 0.18, P = 0.626), and aneuploid embryos (A: 1.23 ± 1.01 vs B: 1.14 ± 0.94, P = 0.592) and aneuploid embryo rate (A: 0.21 ± 0.19 vs B: 0.18 ± 0.15, P = 0.436) were not significantly different in the two groups.

FET outcomes and pregnancy results

The mean of endometrial thickness during FET was 8.71 ± 1.68 mm, which was not different between the two groups (A: 8.98 ± 1.56 mm vs B: 8.64 ± 1.71 mm, P = 0.365). In group A, we had 15 cycles in which the biopsied embryos were transferred to recipients; and in group B, we had 50 cycles. There was no difference in clinical pregnancy rate (A: 73% vs B: 82%, P = 0.476).

Donors and recipients cycles’ outcomes adjusted by the P4/AFC index

To adjust the results of the studied outcomes, we calculated the P4/AFC index of the donors. Two new groups were created using the median of the P4/AFC index as a cut-off point. As exposed in Table 3, Group 1 presented a P4/AFC index < 0.1 (n = 126 cycles) and Group 2 presented a P4/AFC index ≥ 0.1 (n = 133 cycles).

Table 3 Calculated progesterone/antral follicular count index
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In donors’ ovarian stimulation cycles, after calculating this index (Table 4), no significant difference was found between groups 1 and 2 regarding total of used gonadotropins (2769.74 ± 528.96 vs 2836.74 ± 541,45 IU, P = 0.448), basal FSH (5.20 ± 1.78 vs 5.29 ± 1.48 IU/L, P = 0.193), estradiol at trigger 4983.30 ± 3846.34 vs 5549.15 ± 3846.34 pg/mL, P = 0.351), number of retrieved eggs (32.75 ± 13.36 vs 31.77 ± 14.53, P = 0.421), number of MII (24.40 ± 10.86 vs 23.17 ± 12.15, P = 0.188) and MII rate (0.75 ± 0.13 vs 0.72 ± 0.15, P = 0.184).

Table 4 Donors’ cycle outcomes according to P4/AFC index
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After adjusting the statistical analysis according to donors’ AFC, we did not find significant differences between the two groups regarding estradiol at trigger, number of eggs retrieved and number of MII, as we compare Tables 1 and 4.

Regarding recipients’ cycles, after calculating the P4/AFC index (Table 5), we did not observe a significant difference between Groups 1 and 2 in relation to fertilization rate (0.84 ± 0.013 vs 0.81 ± 0.14, P = 0.135), number of blastocysts (3.70 ± 1.47 vs 3.62 ± 1.57, P = 0.623) and number of top-quality embryos (2.25 ± 1.47 vs 2.31 ± 1.47, P = 0.821). Numbers of euploid (2.01 ± 1.22 vs 1.83 ± 1.11, P = 0.288) and aneuploid (1.19 ± 0.99 vs 1.14 ± 0.93, P = 0.674) embryos were similar among groups. There was also no difference in euploidy rate (0.32 ± 0.19 vs 0.28 ± 0.17, P = 0.129) and aneuploidy rate (0.19 ± 0.99 vs 1.14 ± 0.93, P = 0.674). Clinical pregnancy rate was similar in groups 1 and 2 (73% vs 82%, P = 0.476) as shown in Table 5.

Table 5 Recipients’ cycle outcomes according to P4/AFC index
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After adjusting the statistical analysis according to donors’ AFC, we continued to observe no differences between the two groups regarding the analyzed parameters related to fertilization, blastocyst formation, embryo ploidy and clinical pregnancy rate as we compare Tables 2 and 5.

Discussion

Late follicular phase P4 elevation (LFPE) occurs in up to 46% of patients who undergo IVF stimulation [11]. The effect of this premature P4 elevation on clinical and laboratory results of IVF treatments continues to be a theme of debate during the past decades. In an era of freeze-all, PGT-A and FET cycles, with an increasing number of treatments using donated eggs, understanding the effects of serum P4 on embryo quality and ploidy is extremely important, especially in egg donated cycles, in which LFPE is a commonly observed phenomenon during controlled ovarian hyperstimulation due to a high ovarian reserve of these patients.

To our knowledge, this is the first study to evaluate the influence of P4 on embryo ploidy in egg donated cycles. Our findings suggest that elevated donor P4 values on day of trigger may not affect embryo ploidy or embryo euploidy rate in ICSI PGT-A cycles using frozen donated oocytes. We also found that P4 values on day of trigger were not associated with impaired embryo development or worst blastocyst quality parameters in donated egg cycles. Further, high P4 did not show a significant influence on clinical pregnancy following the transfer of euploid embryos to recipients.

Over the years, several studies have described the association between elevated P4 and pregnancy rates. Schoolcraf et al. [21] were the first to report that clinical pregnancy was negatively influenced by serum P4 on the day of hCG administration. These findings were subsequently supported by other studies in the last two decades [11, 17, 22]. The main hypothesis to explain these results is the detrimental effect of high P4 levels on endometrial receptivity. The authors have found that patients with high P4 on trigger day demonstrate a difference in endometrial gene expression and implantation regulating proteins during the traditional window of implantation [23,24,25]. Therefore, it is likely that asynchrony between the embryo and the endometrium in patients with elevated P4 is the mechanism explaining lower pregnancy rates in women undergoing fresh autologous cycles. This assumption was further supported by Shapiro et al. [26] and Baldini et al. [27], who found that P4 elevation on the day of hCG administration did not affect the outcomes of IVF/pregnancy rates after freeze-all strategy followed by FET.

Our data show that P4 elevation did not have a negative impact on ongoing pregnancy rates in egg donated cycles. In our study, by combining PGT-A with FET in oocyte donated cycles, we were able to control the influence of P4 on the endometrium, thus suggesting a deleterious effect of P4 in the endometrium and not in oocyte/embryo quality. A number of other studies performed in oocyte donation programs support the findings we report here. These researches suggest that pregnancy rates of recipients were not negatively influenced by P4 levels of the donors on day of trigger [28,29,30].

Although the detrimental effect of high P4 levels on endometrial physiology and receptivity is well established in the published literature, controversy continues to exist regarding the effect of elevated P4 on oocyte and embryo quality. Some studies that evaluated the impact of supraphysiological P4 on embryonic quality through morphological classification suggested that embryo quality was negatively correlated with P4 levels during ovarian stimulation [31,32,33]. However, it is important to highlight that the generalization of these results is problematic since these studies analyzed embryos at cleavage stage and/or had a small sample for statistical analysis [31]. Our study, on the other hand, only included in its analysis frozen oocytes that where fertilized and that developed to blastocyst stage. Our data showed no association between high P4 and oocyte maturity rate, fertilization rate, number of blastocysts and number of top-quality embryos, suggesting that elevated P4 did not have a negative impact on embryo development nor on blastocyst quality. Our results are consistent with several other studies that also have not reported a negative association between P4 and embryo quality [20, 22, 34,35,36,37,38]. Our findings are also in agreement with other studies performed in oocyte donation programs that did not demonstrate an association between P4 and embryo quality [20, 28, 29].

This inconsistency regarding P4 and oocyte/embryo quality may be due to different P4 cut-off values and discrepancies regarding P4 measurements. A recent meta-analysis of 63 studies involving over 60.000 cycles [11] showed that the P4 threshold value on day of trigger and the methodology used for P4 mensuration varied among the papers. Although there is no consensus on the P4 cut-off, a serum P4 level of 1.5 ng/ml on the day of hCG administration seems to be the most consensual threshold to define detrimental levels of P4 for the outcome of IVF/ICSI–ET cycles [17]. Therefore, for our analysis, a cut-off value of 1.5 ng/mL was adopted. Since there is difficulty in interpreting and comparing results between different studies due to multiple factors directly associated with the method of measuring P4, for our analysis, we sought to eliminate this confounding bias by evaluating all P4 samples in the same laboratory, using a reliable assay that was consistently used under identical conditions and within the same relative time interval when monitoring donors’ ovarian stimulation.

Another point of controversy regarding the effect of P4 and oocyte/embryo quality is the discrepancy between P4 serum levels and intra-follicular values [38]. Shufaro et al. [39] discussed the origin of elevated blood P4 and proposed a new index to measure it based on average P4 secretion per follicle rather than total blood P4. These considerations raise the question that may be P4 intra-follicular measurement per follicle is a more appropriate method than blood measurement since this is a representation of the intrinsic follicular properties [39]. Since it is already well documented that serum P4 level on trigger day in IVF cycles is significantly correlated with the number of follicles and number of oocytes [13], our outcomes were analyzed after correcting the statistical results considering the AFC of the donors in order to avoid bias.

The influence of P4 on embryo ploidy is a topic that only recently has been questioned. Experimental evidence demonstrates the presence of membrane receptors with high affinity for P4 (PGRMC1) in many cells of the mammalian reproductive system [15]. In the ovary, studies on animals support the hypothesis that PGMRC1 affects oocyte biology both extrinsically through the regulation of follicular growth, and intrinsically, during oocyte maturation [16]. According to a recent review in bovine oocytes, PGRMC1 appears to participate in key mechanisms that control the progression of meiosis and that are essential at promoting the adequate completion of oocyte maturation [16]. Evidence suggests that these receptors also have a role in regulating early embryonic development [16]. Such findings suggest an important role of P4, via the PGRMC1 receptor, in oocyte maturation, more specifically related to the mechanism of chromosome segregation during meiosis [16].

Based on experimental evidence, the hypothesis of our study was that extra-physiological P4 during ovarian stimulation in IVF could interfere with oocyte maturation, via specific membrane receptors present in oocytes, leading to a higher rate of aneuploidy. Despite these findings in animal models, our study showed no deleterious effect of high P4 in human embryo ploidy. Our results suggest that possible disturbances in P4 values do not influence the final stages of oocyte maturation and do not have an impact in the meiotic process by increasing the risk of a non-disjunction error via specific oocyte membrane receptors. Our results are consistent with recent studies [12,13,14] that also describe no correlation between P4 values and human embryo ploidy. Due to these differences in results between human and animal models, future studies evaluating gene expression pathways and the molecular dynamics of human embryo division in a non-physiological hormonal environment during ovarian stimulation are most needed to evaluate the real effect of premature P4 elevation on oocyte fertilization, embryonic development and reproductive potential on humans.

A limitation of the existing studies in literature that evaluated the relationship between serum P4 and human embryo ploidy [12,13,14] is the fact that none of them included in their design the analysis of oocyte donors. Thus, they investigated a heterogeneous IVF population. Their results come from embryos generated from infertile women, whose oocyte quality could be impaired due to different types of infertility. On the other hand, our data focused on donors, presumably young fertile women, in whom we expect good-quality oocytes and low chromosome abnormalities rates [10]. Another limitation of the studies [12,13,14] that analyzed the effect of serum P4 levels on human embryo ploidy is the fact that the authors only compared the results using the adopted P4 cut-off value. Contrary to this, to avoid bias, our analysis was adjusted by comparing the groups according to the P4/AFC index.

Furthermore, studies using egg donors as a control population have demonstrated that rates of preimplantation embryo aneuploidy vary between different IVF centers by up to 40% [10]. This suggests that site-specific conditions, in the clinic, in IVF techniques, in the laboratory or in the used medications for ovarian stimulation, could influence chromosomal dynamics [9]. Variables including culture and medium, pH, temperature, osmolarity, and oxygen concentration may all be possible factors influencing chromosomal integrity [9]. Also, laboratory techniques, insemination method, use of laser or manipulation of biopsied cells could also influence genetic results [13]. Since some studies [9, 10] have suggested that factors involved in IVF treatments could interfere with oocyte maturation, embryo development and aneuploidies rates, our study was conducted in a single center, where laboratory conditions, ovarian stimulation protocol, fertilization method and embryo biopsy technique were the same in all analyzed cycles.

Our study is not without limitations. This is a retrospective study were conclusions were taken based on observational data, although we only included PGT-A followed by FET in oocyte donated cycles in order to reduce the chances of bias. Another limitation was the fact that we used two PGT-A methods on trophectoderm biopsy: CGH and NGS. Although we had a little number of biopsied embryos analyzed by CGH, literature shows that little discrepancies may exist when comparing the two technologies [40].

Conclusion

In summary, our study suggests that elevated P4 values on trigger day did not affect embryo ploidy or embryo quality parameters in egg donated cycles. Multicentric studies, with a larger sample, would be desirable to confirm our findings. Considering the increasing number of cycles using donated oocytes over the years, our data should be of interest to the ART community. Furthermore, future studies evaluating the molecular dynamics of embryo division during ovarian stimulation in IVF treatments should elucidate the real effect of premature P4 elevation on oocyte maturation and embryonic development. In this context, the proposal of a new evaluation index based on intra-follicular P4 and not just serum P4 is also an important point to be considered.

Finally, more studies correlating different factors involved in IVF treatments and embryo ploidy are needed to fully understand other causes of aneuploidy rather maternal age. Despite the high frequency of human aneuploidy in older women and its clinical and economic importance, the mechanisms involved in chromosomal abnormalities are not completely known. This elucidation should provide opportunities for improving laboratory and clinical IVF outcomes.