Abstract
Purpose
An impact of different gonadotrophins selection for ovarian stimulation (OS) on oocyte competence has yet to be defined. In this study, we asked whether an association exists between OS protocol and euploid blastocyst rate (EBR) per metaphase-II (MII) oocytes.
Methods
Cycles of first preimplantation genetic testing for aneuploidies conducted by women ≥ 35 years old with their own metaphase-II oocytes inseminated in the absence of severe male factor (years 2014–2018) were clustered based on whether recombinant FSH (rec-FSH) or human menopausal gonadotrophin (HMG) was used for OS, then matched for the number of fresh inseminated eggs. Four groups were outlined: rec-FSH (N = 57), rec-FSH plus rec-LH (N = 55), rec-FSH plus HMG (N = 112), and HMG-only (N = 127). Intracytoplasmic sperm injection, continuous blastocyst culture, comprehensive chromosome testing to assess full-chromosome non-mosaic aneuploidies and vitrified-warmed euploid single embryo transfers (SETs) were performed. The primary outcome was the EBR per cohort of MII oocytes. The secondary outcome was the live birth rate (LBR) per first SETs.
Results
Rec-FSH protocol was shorter and characterized by lower total gonadotrophin (Gn) dose. The linear regression model adjusted for maternal age showed no association between the Gn adopted for OS and EBR per cohort of MII oocytes. Similarly, no association was reported with the LBR per first SETs, even when adjusting for blastocyst quality and day of full blastulation.
Conclusion
In view of enhanced personalization in OS, clinicians shall focus on different endpoints or quantitative effects related to Gn action towards follicle recruitment, development, and atresia. Here, LH and/or hCG was administered exclusively to women with expected sub/poor response; therefore, we cannot exclude that specific Gn formulations may impact patient prognosis in other populations.
Supplementary Information
The online version contains supplementary material available at 10.1007/s10815-022-02684-w.
Keywords: Oocyte competence, Gonadotrophin, Ovarian stimulation, Euploid blastocyst, Live birth
Introduction
The large number of oocytes retrieved after ovarian stimulation (OS) is believed by some to be associated with higher cumulative live birth delivery rate (CLBdR) [1–3], one measure of ART efficacy in a modern IVF clinic [4, 5]. The improved performance of the IVF laboratory, i.e. intracytoplasmic sperm injection (ICSI), blastocyst culture, embryo biopsy for chromosomal testing and especially oocyte/embryo vitrification, allowed the clinicians to fine-tune OS to fully exploit each patient’s ovarian reserve. Nevertheless, although the quantity of oocytes retrieved has key relevance, their competence is even more important. In this regard, the most comprehensive embryological outcome available at present is the euploid blastocyst rate (EBR) per cohort of metaphase-II (MII) oocytes inseminated. This is a parameter accounting for fertilization, blastulation and euploidy rates, thus outlining both the intrinsic quality of a cohort of oocytes and the putative impact of the IVF laboratory. Advanced maternal age (AMA) impacts both blastulation and euploidy rates, thereby affecting the EBR per cohort of MII oocytes [6–8]. Severe male factor (SMF) (defined as oligoasthenoteratozoospermia and azoospermia) [9], instead, could have an impact on fertilization and blastulation rates, with no apparent effect on embryonic chromosomal constitution [9]. Inherent reduced competence may be counterbalanced by increasing the number of oocytes collected, especially in AMA women. With this aim, several personalized OS strategies have been proposed so far, such as pretreatment therapies, LH suppression regimens, different types and starting doses of gonadotrophins (Gn), daily or long-active Gn, LH and/or hCG activity, adjuvant therapies, different types of ovulation trigger or unconventional protocols [10, 11]. If the effectiveness of these strategies to enhance the ovarian response to OS is still a matter of discussion, it is even less clear if they may improve oocyte competence. Across the last decades, some studies in the mouse model claimed that supraphysiological Gn concentrations and oestrogen levels may disturb oocyte maturation and the completion of meiosis, resulting in poorer embryological outcomes and higher aneuploidy rates. However, these data were mainly produced in mouse models [12–14], and the matter in humans is still grounded on few studies conducted within clinical settings currently outdated [15–18]. For instance, in a randomized controlled trial (RCT), it was argued that mild OS protocol would result in fewer oocytes but more euploid embryos than conventional OS [19]; consequently, the authors interrupted their ongoing RCT. However, this assertion was based on the use of 9-chromosome FISH to assess aneuploidies in single blastomere collected from cleavage-stage embryos [19], a workflow very different from the current gold standard for preimplantation genetic testing for aneuploidies (PGT-A). Their claim is debatable also because a recent investigation by Labarta et al. [20] showed comparable euploidy rates across blastocysts obtained after conventional and mild OS cycles in the same egg donor. In 2017, then, the same authors demonstrated that euploidy rates are also independent from Gn dose or ovarian response [21], a result confirmed by others under larger sample sizes [22–25]. In summary, the hypothesis that conventional stimulation may decrease oocyte quality has been extensively confuted [26].
We designed this study to assess a putative association between the Gn chosen for OS and oocyte competence. In particular, we selected a population of AMA women (≥ 35 years), excluded SMF and adopted the EBR per cohort of MII oocytes as a comprehensive measure of oocyte competence. All patients included were matched based on the number of MII oocytes retrieved after antagonist OS conducted with either recombinant FSH (rec-FSH), human menopausal gonadotrophin (HMG) or a combination of both. The cycles were then further clustered in 4 subgroups: rec-FSH only, rec-FSH plus rec-LH, rec-FSH plus HMG and HMG-only. The live birth rate (LBR) per first vitrified-warmed euploid single embryo transfer (SET) and the CLBdR were also assessed in these 4 subgroups.
Materials and methods
Study population and study design
Matched case–control study was performed at a private IVF clinic in Italy (Clinica Valle Giulia, GeneraLife IVF, Rome) including infertile patients undergoing their first ICSI and PGT-A between 2014 and 2018. Starting from 2538 first ICSI and PGT-A cycles with at least one own MII oocyte, we excluded 352 DuoStim cycles, 201 cycles conducted from women younger than 35 years, 302 cycles conducted from male partners affected from SMF (defined as oligoasthenoteratozoospermia and azoospermia) [9], 416 cycles with embryo culture in time-lapse incubators and 211 cycles where sequential media were used. DuoStim was excluded since it entails two ovarian stimulations in the same ovarian cycle [27, 28], while all other features because they are significant confounders on the EBR per cohort of MII oocytes [6, 9, 29]. The remaining 1056 cycles were matched through the propensity score matching function of SPSS based on the number of MII oocytes inseminated in the groups of patients who used rec-FSH, HMG or a combination of both. The 351 matched cycles were clustered in four groups: rec-FSH (N = 57), rec-FSH plus rec-LH (N = 55), rec-FSH plus HMG (N = 127) and HMG-only (N = 112) (Supplementary Fig. 1). The primary outcome was the EBR per cohort of MII oocytes according to the Gn adopted for OS. The main secondary outcome was the LBR per first vitrified-warmed euploid SETs.
IVF protocols and procedures
All patients were treated with GnRH antagonist protocol (cetrorelix, Cetrotide [Merck, Germany]; ganirelix, Orgalutran [Organon, USA], or ganirelix, Fyremadel [Ferring, Switzerland]) with four different Gn regimens: (i) only rec-FSH (150–300 IU/die Gonal-f, [Merck] or Puregon [Organon]), (ii) rec-FSH plus rec-LH (150–300 IU/die Gonal-f or Puregon plus 75–150 IU/die Luveris [Merck] or 150–300 IU/die Pergoveris [Merck]), (iii) rec-FSH plus urinary HMG (150–300 IU/die Gonal-f or Puregon plus 75–150 IU/die Meropur [Ferring] or Meriofert [IBSA Institut Biochimique SA, Switzerland]) and (iv) only urinary HMG (150–300 IU/die Meropur or Meriofert). The type and dose of Gn was selected based on patient characteristics (age, ovarian reserve markers and compliance with the method of administration) and gynaecologist’s evaluation aimed at optimizing the number of oocytes retrieved per OS. Briefly, three different dosages were used based on ovarian reserve and expected ovarian response to OS [30], i.e. 150 IU/die, 225 IU/die and 300 IU/die for expected high, normal and poor responders, respectively. LH and/or hCG activity preparations (i.e. rec-LH or HMG) [31] were administrated to patients with expected sub-optimal or poor response with rec-FSH monotherapy and/or to women whose endogenous LH secretion was profoundly suppressed with GnRH antagonist during OS. After the scan and basal assessment of the ovaries, OS was started on day 2 of the menstrual cycle with a fixed dose of Gn for 4 days. Follicular growth was monitored on day 5 and then every 2 days. Gn doses were adjusted according to the ovarian response, as monitored through the measurement of serum sex steroids and ultrasonography. GnRH antagonist was administered daily after the identification of a leading follicle with a diameter ≥ 13–14 mm and until the day of ovulation trigger. Final maturation of the follicles was induced by the administration of 10,000 IU of hCG (Gonasi, IBSA) or a single subcutaneous bolus of GnRH agonist (50 IU buserelin [Sanofi-Aventis, Canada] or 0.3 mg triptorelin [Decapeptyl, Ferring]) when three follicles reached an average diameter > 17–18 mm. Transvaginal ultrasound, serum oestradiol and LH concentrations, if required, were used to monitor the cycle. Oocyte retrieval was performed under vaginal ultrasound guidance 35 h after hCG trigger.
Laboratory protocols
The procedures for oocyte retrieval, ICSI, embryo culture, trophectoderm biopsy, vitrification and warming have all been described previously in detail [6, 32, 33]. Briefly, all embryos were cultured in a controlled humidified atmosphere (37 °C, 6% CO2 and 5% O2) in standard incubators with continuous single culture medium (CSCM; Irvine Scientific, USA) up to the fully expanded blastocyst stage. Trophectoderm biopsy was conducted without zona pellucida drilling in day 3. All blastocysts were vitrified before they re-expanded after biopsy. Comprehensive chromosome testing (CCT) via quantitative polymerase chain reaction (qPCR) or next-generation sequencing (NGS) was conducted to report uniform non-mosaic whole-chromosome aneuploidies [34, 35] at an external genetic laboratory (Igenomix, Italy). When at least one blastocyst was diagnosed euploid, vitrified-warmed SETs were conducted after (i) a general assessment of patient health status encompassing thyroid, coagulation and immunological screening; (ii) gynaecologic evaluation, including ultrasound exam to exclude intracavitary conditions (e.g. polyps, myoma, septate uterus, endometrial fluid in the uterine cavity, hydrosalpinx) and vaginal swabs; (iii) breast examination; and (iv) infectious disease tests before scheduling embryo transfer (as detailed previously in [7]). After transvaginal ultrasound between days 2 and 3 of the menstrual cycle was conducted to evaluate the endometrial thickness and basal state of the ovaries, endometrial preparation was started through either an artificial protocol or a modified natural protocol [36]. Institutional review board (IRB) approval was obtained from Clinica Valle Giulia for the retrospective analysis of the data.
Statistical analysis
Statistical analyses were conducted through SPSS (IBM, USA; version 27). Continuous data were reported as mean ± standard deviation (SD). After investigating the Gaussian distribution of the data with the Shapiro–Wilk test, we adopted either one-way ANOVA or the Kruskal–Wallis test to assess significant differences. Post hoc analysis was conducted to assess significant differences between groups. Categorical data were reported as ratios, with percentages, and 95% CI for the main outcomes. Chi-squared tests were conducted to assess significant differences. To further confirm the results, (i) generalized linear models adjusted for confounders were used to investigate the association between the Gn adopted for OS and the primary outcome, and (ii) multivariate logistic regression analyses adjusted for confounders were used to investigate the association between the Gn adopted for OS and the LBR per euploid blastocyst transfer. The main features investigated as putative confounders were maternal/paternal age, previous LB, cause of infertility, basal AMH, duration of OS, dose of Gn and CCT method. For the LBR after first vitrified-warmed euploid SETs, also blastocyst quality (defined according to Gardner and Schoolcraft’s criteria [37]), day of full blastulation (5, 6 or 7) and endometrial preparation protocol were investigated as putative confounders. Also, CLBdR per completed cycle (i.e. LB achieved or no transferable blastocyst obtained/left) was reported as defined by the ICMART [38, 39]. All cycles were completed when we drafted the manuscript. A p value set at 0.05 was considered statistically significant. We estimated that the sample size needed to exclude a medium association (effect size: 0.25) between the Gn adopted for OS and the EBR per cohort of MII oocytes with an 85% power and a p value = 0.05 was at least 51 cycles per group (G*Power v3.1).
Results
The main couples’ characteristics in each group are shown in Table 1 clustered according to the Gn adopted for OS. The data outline a population of AMA women (mean maternal age > 40 years in all groups) collecting on average 6.4 ± 4.4 MII oocytes (matching feature). As expected, the only significant differences in the groups were a longer OS when HMG was used and a higher total dose of Gn when LH and/or hCG activity was added. These data support a proper post-OS matching of the couples included in the 4 study groups.
Table 1.
Couple clustered in the 4 groups according to the gonadotrophin (Gn) adopted for ovarian stimulation (OS)
| Rec-FSH (N= 57) | Rec-FSH + Rec-LH (N= 55) | Rec-FSH + HMG (N= 127) | HMG (N= 112) | p value | |
|---|---|---|---|---|---|
| Maternal age, mean ± SD (years) | 40.0 ± 2.5 | 40.6 ± 2.5 | 40.7 ± 2.5 | 40.8 ± 2.7 | 0.14 |
| Paternal age, mean ± SD (years) | 42.9 ± 5.0 | 44.3 ± 7.0 | 42.6 ± 4.8 | 42.6 ± 5.5 | 0.23 |
| Main cause of infertility, N (%) | |||||
| Idiopathic | 40 (70) | 44 (80) | 106 (84) | 92 (82) | 0.35 |
| Endometriosis | 5 (9) | 4 (7) | 5 (4) | 3 (3) | |
| Endocrine-ovulatory | 2 (4) | 0 (–) | 1 (1) | 4 (4) | |
| Tubal | 10 (17) | 7 (13) | 15 (12) | 13 (12) | |
| Previous LB(s), N (%) | |||||
| Yes | 13 (23) | 13 (24) | 20 (16) | 17 (15) | 0.37 |
| No | 44 (77) | 42 (69) | 107 (84) | 95 (85) | |
| AMH, mean ± SD (ng/ml) | 1.8 ± 2.2 | 1.7 ± 1.4 | 1.7 ± 1.8 | 1.8 ± 1.6 | 0.85 |
| Sperm factor, N (%) | |||||
| Normozoospermic | 32 (56) | 32 (58) | 80 (63) | 69 (62) | 0.81 |
| 1–2 defects | 25 (44) | 23 (42) | 47 (37) | 43 (38) | |
| Days of OS, mean ± SD | 9.7 ± 1.9 | 9.4 ± 1.5 | 9.9 ± 1.7 | 10.2 ± 1.8 |
Rec-FSH vs HMG < 0.05 Rec-FSH + Rec-LH vs HMG < 0.05 All other comparisons = NS |
| Total dose of Gn, mean ± SD (IU) | 2615 ± 977 | 3601 ± 1189 | 3818 ± 945 | 2891 ± 911 |
Rec-FSH vs HMG = NS All other comparisons < 0.05 |
| COCs, mean ± SD | 9.4 ± 7.3 | 9.3 ± 6.2 | 9.0 ± 6.3 | 9.2 ± 6.4 | 0.99 |
| MII oocytes inseminated, mean ± SD | Matching variable: 6.4 ± 4.4 | – | |||
MII metaphase-II, LB live birth, COC cumulus oocyte complex
The EBR per cohort of MII oocytes, namely our primary outcome, was reported according to the Gn adopted for OS within 4 ranges of maternal age at oocyte retrieval (in women aged 35–37 years, 38–39 years, 40–41 years and ≥ 42 years, the average EBR per cohort of MII oocytes was 25.6% ± 24.3%, 18.4% ± 20.6%, 11% ± 15.9% and 3.6% ± 8.6%, respectively), and no difference was reported by the ANOVA test, as confirmed also by the generalized linear model adjusted for maternal age (partial eta-squared = 0.014, power = 0.42 and p value = 0.18) (Fig. 1).
Fig. 1.
Boxplots reporting the euploid blastocyst rate per cohort of metaphase-II (MII) oocytes according to the gonadotrophins (Gn) adopted for ovarian stimulation (OS) within different ranges of maternal age at oocyte retrieval. The dotted black lines outline the average (avg.) value per cluster of maternal age. The one-way ANOVA highlighted no significant difference in the 4 groups. The generalized linear model adjusted for maternal age confirmed the absence of a significant association between the Gn adopted for OS and the primary outcome under investigation (partial eta-squared = 0.014, power = 0.425 and p value = 0.18)
Similarly, the LBR per first vitrified-warmed euploid SET was not associated with the Gn adopted for OS (N = 14/33, 42%, 95% CI 26–61%, for rec-FSH; N = 9/22, 41%, 95% CI 21–63%, for rec-FSH plus Rec-LH; N = 28/62, 45%, 95% CI 33–58%, for rec-FSH plus HMG; and N = 24/55, 44%, 95% CI 31–58%, for HMG) as confirmed by both univariate and multivariate logistic regression analyses adjusted for blastocyst quality and day of full blastulation (Table 2).
Table 2.
Live birth rate (LBR) per first vitrified-warmed single euploid blastocyst transfer according to ovarian stimulation (OS) protocol
| Variable | LBR (ratio, %) | Univariate OR (95% CI), p value | Multivariate OR (95% CI), adjusted p value |
|---|---|---|---|
| OS protocol | |||
| Rec-FSH | 14/33, 42 | Control | Control |
| Rec-FSH + Rec-LH | 9/22, 41 | 0.94 (0.31–2.8), p = 0.9 | 0.94 (0.3–3.0), p = 0.9 |
| Rec-FSH + HMG | 28/62, 45 | 1.12 (0.48–2.6), p = 0.8 | 1.20 (0.49–3.0), p = 0.7 |
| HMG | 24/55, 44 | 1.05 (0.44–2.51), p = 0.9 | 0.97 (0.39–2.4), p = 0.9 |
| Blastocyst qualitya | |||
| ≥ BB | 72/157, 46 | Control | Control |
| < BB | 3/15, 20 | 0.30 (0.08–1.09), p = 0.07 | 0.48 (0.11–2.0), p = 0.3 |
| Day of full blastulation | |||
| 5 | 44/77, 57 | Control | Control |
| 6 | 27/77, 35 | 0.40 (0.21–0.78), p < 0.01 | 0.41 (0.21–0.79), p < 0.01 |
| 7 | 4/18, 22 | 0.21 (0.07–0.71), p = 0.01 | 0.26 (0.07–0.98), p = 0.05 |
As expected, because of the matching strategy and due to the absence of an OS-derived impact on oocyte competence, the CLBdR was also similar in the four matched study groups (N = 17/57, 29.8%, 95% CI 19–44%, with rec-FSH; N = 14/55, 25.5%, 95% CI 15–39%, with rec-FSH plus rec-LH; N = 34/127, 26.8%, 95% CI 19–35%, with rec-FSH plus HMG; and N = 33/112, 29.5%, 95% CI 21–39%, with HMG; p = 0.9).
Discussion
The potential impact of IVF on embryo euploidy rates has been investigated in several studies across the last decade, mainly focused on laboratory practice and protocols, like the insemination method (e.g. [41–43]), the use of oocyte vitrification (e.g. [44, 45]) or the culture media (e.g. [29, 46]). But, OS is a cornerstone of IVF and perhaps the main step of patient journey that can be personalized to enhance IVF success per cycle. Previous studies suggested that Gn dose and consequent ovarian response may not impact the euploidy rates [21–25]. In fact, more oocytes retrieved (and more embryos obtained) reflect higher chance to find at least one euploid blastocyst for transfer [21, 47]. Similarly, other features of OS have been assessed for a putative impact on oocyte competence, such as the kind and the timing of ovulation trigger [48–50], the use of progestins to block LH surge [51, 52] and the phase of the ovarian cycles at which OS is started [53]. Still, the relationship between the type of Gn adopted and oocyte EBR remains a challenge to be further investigated. In fact, to the best of our knowledge, this is the first study aiming at outlining whether an association exists in a well-defined setting grounded on the maximization of ovarian response via antagonist protocol, ICSI, blastocyst culture, trophectoderm biopsy, comprehensive chromosome testing and cycle segmentation. As exclusion criteria, we adopted the main features per se associated with the fertilization and/or blastulation rates, such as woman age lower than 35 years, SMF (i.e. oligoasthenoteratozoospermia and azoospermia), abnormal parental karyotypes, the use of time-lapse incubators and sequential culture media [6, 9, 29]. The rec-FSH and HMG groups were finally matched for the number of MII oocytes inseminated. This design allowed us to minimize the risk for bias on our outcome measures and focus exclusively on the effect of the Gn adopted for OS. Our results increase the body of evidence regarding antagonist protocols and provide additional information on outcomes poorly described previously in the literature. Specifically, when adjusting the data for maternal age, no association was reported with the EBR per cohort of inseminated MII oocytes. In our study, also the LBR per first vitrified-warmed euploid single blastocyst transfer was unaffected from the Gn adopted for OS, even after adjusting for blastocyst quality and day of full blastulation. As a result of both (i) a proper definition of the matching criteria and (ii) the reported absence of an OS-derived impact on oocyte competence, also the CLBdR was similar in the four study groups. However, our investigation is not suitable to assess such critical outcome per intention to treat, a purpose that should rather involve patient matching prior to OS.
Notably, OS duration was shorter and the total Gn dose was lower in the rec-FSH groups and, even when adjusted for confounders, LH and/or hCG activity supplemented through rec-LH or HMG did not affect oocyte competence. If on the one hand this last result is reassuring, since such supplementation is administered mainly to improve follicle recruitment and development in poor prognosis patients [54–56], and on the other hand we encourage further investigations to confirm our results, that should be evaluated considering their limitations.
Limitations
To assess the impact of the Gn used during OS on endpoints potentially perturbed by several variables (e.g. patient-specific genetic background), a larger sample size is required. For instance, especially, LH and hCG activities did result in different outcomes in a previous meta-analysis on a large overall number of women [57]. The strict inclusion criteria adopted here (e.g. only first PGT-A cycles conducted in AMA women in the absence of SMF) and the matching based on the number of MII oocytes retrieved were indeed exploited to counterbalance the intrinsic limitations of a retrospective design. With this matching strategy, we could compare oocyte EBR in homogenous small groups of patients clustered according to the Gn adopted for OS and with enough power to exclude a medium-level association.
Importantly, the effect of LH and/or hCG molecules was evaluated after being administered to patients with expected sub-optimal or poor response, while optimal responders underwent FSH monotherapy. Therefore, our analysis assumed that follicles from ovaries of sub/poor responders and normoresponders may lead to qualitatively similar mature oocytes, although this assumption must yet be confirmed. In other terms, our results describe the non-inferiority of rec-LH or HMG supplementation in the context of poor/sub response against FSH monotherapy in normoresponders, i.e. a setting that mirrors the real-life scenario of most patients undergoing IVF.
A last consideration is that the choice of the Gn administered to each patient was not random, but it was based on gynaecologists’ judgement, patient compliance to the different medical devices and drug reimbursement policies applied in each couple’s administrative area. RCTs are therefore required to confirm our data.
From a molecular perspective, mitotic aneuploidies cannot be diagnosed on a single trophectoderm biopsy [58–62]; thus, we could not assess a potential impact of OS on post-zygotic chromosomal missegrations permissive towards blastocyst development. Several previous studies analysed human blastocysts donated to research and disaggregated in their inner cell mass and multiple trophectoderm sections, overall reporting an average 5% prevalence of euploid-aneuploid mosaicism [58, 59, 63]. In the future, academic research conducted with that same design and including embryos obtained after different OS protocols may provide hard data to investigate a putative association with chromosomal mosaicism. Conversely, when produced in the clinical setting, this information cannot be considered reliable.
Conclusion
These results extend our understanding of the effects of different OS strategies on oocyte quality. They allowing clinicians to focus on the quantitative effects of Gn on follicle recruitment, development, and atresia. Considering this, Future studies should be designed to define Gn most suitable to any specific patient population. For instance, genetic assessment of Gn receptor polymorphisms may represent an interesting field of investigation in this context. Although we report no effect of the Gn chosen for OS on the EBR of the oocytes retrieved, we speculate that through different biochemical intrafollicular effects during the last stages of folliculogenesis, they may improve (or impair) ovarian sensitivity, thereby impacting patient prognosis.
Supplementary Information
Below is the link to the electronic supplementary material.
Supplementary file1 Supplementary Fig. 1 Study flowchart. PGT-A, preimplantation genetic testing for aneuploidies; MII, metaphase II; TLI, time-lapse incubator; rec-FSH, recombinant FSH; HMG, human menopausal gonadotropin; rec-LH, recombinant LH; LBR, live birth rate; SET, single embryo transfer. (PDF 60 KB)
Author contribution
AV, DC, LR and FMU designed the study. DC, FI and MGA conducted the statistical analyses. AV, CS, DC and FI drafted the manuscript. All authors contributed to the collection, analysis and discussion of the data and revised and approved the manuscript.
Declarations
Conflict of interest
The authors declare no competing interests.
Footnotes
Publisher's note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
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Supplementary Materials
Supplementary file1 Supplementary Fig. 1 Study flowchart. PGT-A, preimplantation genetic testing for aneuploidies; MII, metaphase II; TLI, time-lapse incubator; rec-FSH, recombinant FSH; HMG, human menopausal gonadotropin; rec-LH, recombinant LH; LBR, live birth rate; SET, single embryo transfer. (PDF 60 KB)