Analiză comparativă între FSH recombinant și gonadotropina umană de menopauză privind profilul embrionar și eficiența gonadotropinelor în ciclurile de FIV: studiu de cohortă cu potrivire

Introduction

Infertility, a condition defined by the World Health Organization (WHO) as the inability to conceive after 12 months or more of regular, unprotected sexual intercourse, affects approximately 15% of couples worldwide⁽¹⁾. In India, the burden is estimated to be even higher due to delayed marriage, lifestyle changes, environmental exposures and increased prevalence of ovulatory disorders and endometriosis⁽²⁾. With declining fertility trends, assisted reproductive technology (ART) has become an indispensable component of infertility treatment, offering hope to millions of couples globally. Among the many steps involved in ART, controlled ovarian stimulation (COS) is fundamental. The primary aim of COS is to induce the growth of multiple follicles to retrieve a higher number of oocytes, thereby improving the likelihood of generating high-quality embryos and achieving successful implantation and live birth⁽³⁾. The success of controlled ovarian stimulation depends significantly on the choice, dosage and biological response to gonadotropin stimulation. Two widely used pharmacological options are recombinant follicle-stimulating hormone (rFSH) and human menopausal gonadotropin (hMG)⁽⁴⁾. Recombinant FSH, produced through recombinant DNA technology, is characterized by high purity and consistency, with negligible luteinizing hormone (LH) activity. It mimics the endogenous FSH hormone and acts selectively on ovarian granulosa cells to stimulate follicular development⁽⁵⁾. On the other hand, hMG is a urinary-derived preparation containing both FSH and LH activity. Though it is less pure and biologically variable compared to rFSH, the presence of LH activity may support certain physiological processes in folliculogenesis⁽⁶⁾. These inherent differences have led to ongoing debate regarding the superiority of one over the other in terms of clinical outcomes, safety and cost-effectiveness. Previous randomized and observational studies have compared rFSH and hMG in terms of oocyte yield, pregnancy rates and live birth outcomes^(7-9). However, the results have often been conflicting, and the majority of available literature has focused on clinical endpoints, without giving equal attention to intermediate embryological outcomes, such as embryo quality and grade, which play a crucial role in determining the overall success of ART cycles^(10,11). In particular, the number of Grade A embryos – those with ideal blastomere number, symmetry and minimal fragmentation – serves as a validated surrogate marker for implantation potential and cumulative pregnancy rates⁽¹²⁾. Additionally, there is a growing concern regarding the economic burden of ART, especially in low- and middle-income countries (LMICs), where treatments are often paid for out-of-pocket and remain inaccessible to many patients⁽¹³⁾. In this context, treatment efficiency – defined not just by success rates, but by the amount of drug used per unit biological output – has emerged as a crucial metric. Despite this, few studies have systematically evaluated the gonadotropin efficiency, particularly in terms of cost and dose required to obtain high-quality embryos. To address these gaps, we designed a retrospective cohort study comparing embryo profile outcomes between women stimulated with rFSH versus hMG. By utilizing a matched cohort design based on age, Body Mass Index (BMI), antral follicle count (AFC) and hormonal parameters, we aimed to minimize the confounding effects seen in previous studies. More importantly, we introduce a novel outcome measure – the Gonadotropin Efficiency Index (GEI) –, defined as the number of international units (IU) required to generate one Grade A embryo. Furthermore, we evaluated the cost per Grade A embryo based on real-world pricing of gonadotropins in India, making the findings not only scientifically relevant but also economically actionable. This study, therefore, provides a more nuanced, embryo-centered and cost-conscious comparison of two major stimulation protocols in IVF. The findings are expected to guide individualized stimulation choices based on ovarian reserve, embryo quality potential and patient-specific financial considerations.

Materials and method

Study design and setting

This was a retrospective matched cohort study conducted at a tertiary-level fertility center in Western India. The study included patients who underwent controlled ovarian stimulation for IVF/ICSI cycles between January 2022 and December 2023.

Ethical approval

The study protocol was reviewed and approved by the Institutional Ethics Committee. Due to the retrospective nature, individual informed consent was waived, and confidentiality of patient data was strictly maintained.

Study population and inclusion criteria

Women aged 21-45 years old, who underwent IVF or ICSI using either recombinant FSH (rFSH) or human menopausal gonadotropin (hMG) for ovarian stimulation, were eligible. Only cycles with complete clinical and embryological records were included.

• Exclusion criteria:
• Mixed gonadotropin protocols (combined rFSH and hMG).
• Oocyte cryopreservation cycles.
• Incomplete or missing embryo development data.
• Donor oocyte cycles.

Cohort matching

To reduce baseline confounding, 150 patients from each group (rFSH and hMG) were matched 1:1 based on:

• Age (±2 years old).
• Body Mass Index (±2 kg/m²).
• Antral Follicle Count (±2 follicles).
• Day 2 serum FSH level (±1.5 mIU/mL).
• Stimulation protocol (GnRH agonist or antagonist).

Matching was performed manually using a stratified search filter in the institutional electronic records system.

Ovarian stimulation protocol

Stimulation protocols were individualized based on age, ovarian reserve and clinician preference. Patients received either rFSH (Gonal-F®, Merck Serono or equivalent), or hMG (Menotas®, Intas or equivalent).

Follicular development was monitored by transvaginal ultrasound. Ovulation was triggered using recombinant hCG when at least three follicles ≥18 mm were observed. Oocyte retrieval was performed 36 hours later, followed by IVF or ICSI based on semen parameters.

Outcome measures

The following outcomes were analyzed and compared between the two groups.

Embryological outcomes:

• total number of oocytes retrieved
• number of mature (MII) oocytes
• fertilization rate (%).
• number of embryos formed
• number of Grade A embryos (based on Istanbul consensus criteria⁽¹²⁾).

Stimulation characteristics:

• total gonadotropin dose (IU)
• duration of stimulation (days).

Efficiency metrics

Gonadotropin Efficiency Index (GEI)

GEI=Total IU of gonadotropin used/Number of Grade A embryos formed.

Cost per grade A embryo

Estimated Cost (INR) = (Total IU/ 75) ×Unit Cost per 75 IU.

Market price assumptions (2025):

• rFSH –13 USD per 75 IU.
• hMG – 4 USD per 75 IU.

Statistical analysis

Data analysis was performed using SPSS version 25.0 (IBM Corp, Armonk, NY, USA). The Kolmogorov-Smirnov test was used to assess normality of distribution. Continuous variables were expressed as mean ± SD or median (IQR) and compared using independent t-test or Mann-Whitney U test. Categorical variables were compared using Chi-square or Fisher’s exact test. A p-value

Results

1. Baseline characteristics

The rFSH and hMG groups each comprised 150 patients after 1:1 matching based on age, BMI, AFC, day 2 FSH levels and stimulation protocol. Baseline characteristics were statistically comparable between groups, confirming effective matching (Table 1).

2. Embryological outcomes

Patients stimulated with rFSH had significantly better embryo profile outcomes than those receiving hMG (Table 2). Median values for oocyte yield, maturity, embryo number and Grade A embryos were all higher in the rFSH group.

3. Gonadotropin efficiency and cost

Despite a higher per-IU cost, rFSH showed superior efficiency in terms of IU required per Grade A embryo, and a lower total cost per Grade A embryo.

Interpretation:

• rFSH produced significantly more total and high-quality embryos per patient
• GEI was nearly 3.6 times better in the rFSH group.

Despite the higher unit cost, rFSH was more cost-efficient per Grade A embryo than hMG in this matched cohort.

The rFSH group had a substantially lower GEI (median ~346 IU/Grade A embryo) compared to the hMG group (median ~1254 IU/Grade A embryo). A lower GEI value indicates greater stimulation efficiency – i.e., fewer gonadotropin units were needed to produce each Grade A embryo. This suggests that, despite the higher cost per IU, rFSH is significantly more efficient biologically in producing top-quality embryos per unit of gonadotropin used, as shown in Figure 1.

Discussion

This matched retrospective cohort study evaluated the comparative performance of recombinant FSH (rFSH) and human menopausal gonadotropin (hMG) in controlled ovarian stimulation (COS) for IVF/ICSI cycles, focusing on embryological parameters, gonadotropin efficiency, and cost per Grade A embryo. Our findings highlight a clear advantage of rFSH over hMG in terms of embryo quality, stimulation efficiency and economic value per high-grade embryo generated.

Comparative efficacy: embryo yield and quality

The data demonstrated that women receiving rFSH achieved significantly higher numbers of total oocytes retrieved, mature (MII) oocytes and embryos formed, particularly Grade A embryos – a key surrogate marker for embryo competence and implantation potential⁽¹²⁾. These findings align with previous studies suggesting that the more selective action of rFSH on FSH receptors, without LH contamination, may contribute to more synchronized follicular growth and cytoplasmic maturation^(4,5). In contrast, hMG, while containing both FSH and LH activity, may result in less predictable follicular response due to its batch variability and urinary derivation. Some evidence supports its benefit in women with poor ovarian response, where LH bioactivity may assist in androgen-to-estrogen conversion during folliculogenesis⁽⁶⁾. However, in normoresponders, such as the population studied here, this added LH activity may be less critical or even inhibitory to follicular dynamics⁽⁸⁾. Moreover, the fertilization rate and proportion of mature oocytes were modestly higher in the rFSH group, further reinforcing the hypothesis that follicular microenvironment and granulosa cell stimulation quality directly impact downstream embryo competence. These embryological advantages, even in the absence of clinical outcome data, are clinically meaningful, as Grade A embryos have been strongly correlated with improved implantation, reduced miscarriage risk and higher cumulative pregnancy rates⁽¹²⁾.

Gonadotropin Efficiency Index: a novel clinical metric

A unique contribution of this study is the introduction of the Gonadotropin Efficiency Index (GEI) –, defined as the number of International Units (IU) of gonadotropin used per Grade A embryo produced. This measure offers a refined understanding of stimulation efficiency, moving beyond crude metrics such as total oocytes retrieved or cost per cycle. Our results showed a markedly lower GEI in the rFSH group (346 IU per Grade A embryo) compared to hMG (1254 IU), suggesting a 3.6-fold greater efficiency with rFSH. Few studies to date have evaluated COS through this lens. While previous research has documented the dose-response effect of FSH stimulation on oocyte yield⁽¹⁰⁾, most did not adjust for embryo quality. This may have led to under-recognition of how stimulation choice influences the biological efficiency of embryo production. Our results indicate that not all oocytes – or gonadotropin units – are equal, and optimizing stimulation should consider quality-adjusted outcomes.

Economic implications: cost per embryo versus cost per IU

Although rFSH is significantly more expensive per IU compared to hMG (13 USD versus 4 USD per 75 IU in the Indian market), the cost per Grade A embryo was paradoxically lower in the rFSH group (60 USD versus 67 USD). This suggests that rFSH may provide greater value per effective embryo, despite the upfront cost. This insight has substantial implications in low- and middle-income countries (LMICs), where ART cycles are predominantly paid for out-of-pocket, and cost-efficiency is paramount to access. Prior literature often presents hMG as the more “affordable” option without adjusting for biological return on investment^(9,13). By incorporating both dose and outcome into a single cost-efficiency metric, our study challenges that notion and advocates for individualized cost-yield assessments.

Real-world relevance and matching strategy

A notable strength of this study is its use of real-world data and strict 1:1 matching on key biological and demographic variables – age, BMI, AFC and FSH levels – to minimize confounding. Matching allowed for a fair and clinically relevant comparison between groups without relying on artificial stratification or subgroup analyses. Furthermore, the matched design helps avoid the bias that arises when older or diminished ovarian reserve patients are overrepresented in the hMG group, as seen in many retrospective studies⁽²⁾. By holding reserve indicators constant, we were able to attribute the differences in embryo profile and efficiency more confidently to the pharmacological differences between rFSH and hMG.

Limitations

As with all retrospective analyses, certain limitations must be acknowledged. Despite our matching protocol, unmeasured variables such as serum AMH levels or endometrial receptivity may still confound the results. Additionally, implantation rates, clinical pregnancies and live birth outcomes were not included in this analysis. Future studies incorporating these endpoints are warranted to validate the clinical implications of embryo profile advantages. Furthermore, while Indian market prices were used to calculate cost-effectiveness, variations in regional pricing, discounts and insurance coverage may influence generalizability in other settings.

Future directions

Prospective randomized controlled trials are needed to validate the GEI and cost-per-embryo metrics as clinically meaningful outcomes. Incorporating AMH-based or AFC-based stimulation algorithms, rFSH biosimilars and cumulative live birth data will be essential to enhance external validity. There is also scope for pharmacoeconomic modeling and decision-tree cost-benefit analysis, which could aid policy-makers and clinicians in developing stimulation guidelines for different patient subgroups.

Conclusions

In this retrospective matched cohort analysis of wo­men undergoing IVF/ICSI, recombinant FSH (rFSH) demonstrated significantly superior performance compared to human menopausal gonadotropin (hMG) in terms of embryo yield, quality and stimulation efficiency. The introduction of the Gonadotropin Efficiency Index (GEI) provided a novel and meaningful metric to assess cost-adjusted biological response, revealing that rFSH required fewer IU to generate each Grade A embryo. Despite a higher per-unit cost, rFSH resulted in a lower cost per top-quality embryo, underscoring its cost-effectiveness in appropriately selected patients. These findings highlight the importance of evaluating controlled ovarian stimulation not only by clinical outcomes but also by efficiency and economic parameters. Incorporating GEI and cost-per-embryo measures may guide more personalized and resource-conscious stimulation protocols, particularly in low- and middle-income countries, where affordability and embryo quality are equally critical to ART success.

Funding. The study was investigator-initiated and institutionally supported using departmental resources.

Conflict of interests. No financial relationships or affiliations that could influence the interpretation or presentation of this work are reported.

Acknowledgments. The authors would like to thank the embryology and nursing teams for their technical support and meticulous documentation of patient data.

Autor corespondent: Smit Bharat Solanki E-mail: drsmitbharat@gmail.com

CONFLICT OF INTEREST: none declared.

FINANCIAL SUPPORT: none declared.

This work is permanently accessible online free of charge and published under the CC-BY.