Cost-effectiveness of ovarian stimulation agents for IUI in couples with unexplained subfertility

Cost-Effectiveness of Interventions Related to the Treatment of Women With Polycystic Ovary Syndrome: A Scoping Review

Context

Polycystic ovary syndrome (PCOS) affects up to one-in-five reproductive-aged women and its global healthcare-related economic burden is substantial. The aim of this review was to summarise evidence of the cost-effectiveness of interventions related to the treatment of women with PCOS.

Evidence Acquisition

Six academic databases were systematically searched for relevant records. Cost data were extracted, and an interpretation statement was provided for each study based upon the cost difference or incremental cost-effectiveness ratio, and its statistical significance.

Evidence Synthesis

The search yielded 10 relevant studies. Only one study was conducted in a low- and middle-income country (LMIC), China. Nine studies focused on infertility treatment, and one study related to pregnancy care. There remains uncertainty regarding cost-effectiveness of the following infertility treatments: In vitro fertilisation (IVF) cycles compared to ovulation induction (OI) cycles in women with clomiphene citrate (CC) resistant PCOS; and urinary follicle stimulating hormone compared to recombinant follicle stimulating hormone for OI. There are likely cost savings associated with laparoscopic ovarian drilling compared to OI with gonadotropins in women with CC-resistant PCOS, as well as with artificial cycle-frozen embryo transfer (AC-FET) without gonadotropin releasing hormone agonist (GnRH-a) pre-treatment compared to AC-FET with GnRH-a pre-treatment in women with PCOS. Treatment with metformin was lower cost and more effective compared to no treatment for achieving normal glucose regulation without developing gestational diabetes mellitus.

Conclusion

The high proportion of fertility-related treatment studies reflects reproductive features often being the best-recognised feature of PCOS. However, limited evidence is available from LMICs. Further economic evidence is needed regarding PCOS treatments, particularly lifestyle interventions treating outcomes other than infertility.

Is combined letrozole and clomiphene superior to either as monotherapy: a systemic review and meta-analysis based on clinical trials

OBJECTIVE

This research was conducted to assess the therapeutic advantage of combined letrozole and clomiphene citrate versus monotherapy for polycystic ovarian syndrome (PCOS) patients.

STUDY DESIGN

Five databases were searched using the search string: (letrozole and clomiphene) AND (clomiphene OR clomiphene citrate OR CC) AND (letrozole OR LE) AND (ovulation induc* OR fertility induc* OR fertility preserv*) AND (polycystic ovarian syndrome OR PCOS). All statistical analyses were conducted in Review Manager 5.4.1. Random effect-effect model was used to pool risk ratio (RR), mean difference (MD), and odds ratio (OR) and their corresponding 95% confidence interval (CI). Moreover, qualitative analysis was conducted to qualitatively analyze ovulation, secondary outcomes, and cycle characteristics.

RESULTS

One clinical trial and three randomized clinical trials (RCTs) were used in the study. Two studies were used in a quantitative analysis showing that combination was superior for ovulation induction (RR = 1.86 [1.37, 2.53]; p < 0.0001; I2 = 0%), but the number of follicles ≥15 mm was significantly associated with the combination (MD = 0.40[0.14, 0.66]; p = 0.002; I2 = 0%). On subgroup analysis, only hot flushes were significantly associated with the combination (RR = 2.67[1.12, 6.36]; p = 0.03; I2 = 0%). The meta-analysis of two studies reported a significantly higher ovulation rate and number of dominant follicles in the combination therapy group compared with the LE alone arm but no significant difference in pregnancy rate, endometrial thickness, and adverse events.

CONCLUSION

Our study demonstrates a significant effect of the combination on ovulation induction. The combination yielded a better chance of conception and viable pregnancy. Further studies are needed to determine the live birth rate. HighlightsCombined Letrozole and Clomiphene is superior to either of these drugs alone for ovulation induction in PCOS.Our results conclude that the combination results in better ovulation, cycle characteristics, and secondary changes.Only the incidence of hot flushes as an adverse effect is increasingly reported in combination.

Economic evaluation of GnRH-agonist long protocol and GnRH-antagonist protocol in IVT/ICSI among the Chinese population: using pharmacoeconomic models

OBJECTIVE

This paper uses health economics methods to discuss the cost-effectiveness value of long protocol and antagonist protocol for in vitro fertilisation and embryo transfer (ET) in the Chinese population.

DESIGN

Health economic evaluation study.

SETTING

The data needed to construct the model for this study were derived from published studies and other secondary sources in China.

PARTICIPANTS

No patients participated in the study.

MEASURES

The main outcomes were live birth rate (LBR) and cost. From the societal perspective, we considered the direct and indirect costs over the course of the treatment cycles. A cost-effectiveness was measured using the incremental cost-effectiveness ratio and the probability that a protocol has higher net monetary benefit. Sensitivity analysis was carried out to verify the reliability of the simulation results.

RESULTS

For the Chinese population, the long protocol resulted in a higher LBR than the antagonist protocol (29.33% vs 20.39%), but at the same time, it was more expensive (￥29 146.26 (US$4333.17) vs ￥23 343.70 (US$3470.51)), in the case of considering only one fresh ET cycle. It was the same when considering subsequent frozen ET (FET) cycles (51.78% vs 42.81%; ￥30 703.02 (US$4564.62) vs ￥24 740.95 (US$3678.24)). The results of most subgroups were consistent with the results of the basic analysis. However, for certain populations, the long protocol was the inferior protocol (less effective and more expensive).

CONCLUSION

For the Chinese population, when the monetary value per live birth was greater than ￥65 420 (US$9726) and ￥66 400 (US$9872), respectively, considering only one fresh cycle and considering subsequent frozen cycles, the long protocol is the preferred protocol. This threshold also varies for women of different ages and ovarian response capacities. For women in POSEIDON (Patient-Oriented Strategies Encompassing IndividualizeD Oocyte Number) group 2, group 3 and group 4, antagonist protocol is recommended as the preferred protocol. The results of this study need to be verified by further large-scale randomised controlled trials.

Systematic review of the economic evaluation model of assisted reproductive technology

BACKGROUND

With the increasing demand for fertility services, it is urgent to select the most cost-effective assisted reproductive technology (ART) treatment plan and include it in medical insurance. Economic evaluation reports are an important reference for medical insurance negotiation. The aim of this study is to systematically evaluate the economic evaluation research of ART, analyze the existing shortcomings, and provide a reference for the economic evaluation of ART.

METHODS

PubMed, EMbase, Web of Science, Cochrane Library and ScienceDirect databases were searched for relevant articles on the economic evaluation of ART. These articles were screened, and their quality was evaluated based on the Comprehensive Health Economics Evaluation Report Standard (CHEERS 2022), and the data on the basic characteristics, model characteristics and other aspects of the included studies were summarized.

RESULTS

One hundred and two related articles were obtained in the preliminary search, but based on the inclusion criteria, 12 studies were used for the analysis, of which nine used the decision tree model. The model parameters were mainly derived from published literature and included retrospective clinical data of patients. Only two studies included direct non-medical and indirect costs in the cost measurement. Live birth rate was used as an outcome indicator in half of the studies.

CONCLUSION

Suggesting the setting of the threshold range in the field of fertility should be actively discussed, and the monetary value of each live birth is assumed to be in a certain range when the WTP threshold for fertility is uncertain. The range of the parameter sources should be expanded. Direct non-medical and indirect costs should be included in the calculation of costs, and the analysis should be carried out from the perspective of the whole society. In the evaluation of clinical effect, the effectiveness and safety indexes should be selected for a comprehensive evaluation, thereby making the evaluation more comprehensive and reliable. At least subgroup analysis based on age stratification should be considered in the relevant economic evaluation.

Oral follicle-stimulating hormone receptor agonist affects granulosa cells differently than recombinant human FSH

OBJECTIVE

To determine whether TOP5300, a novel oral follicle-stimulating hormone (FSH) receptor (FSHR) allosteric agonist, elicits a different cellular response than recombinant human FSH (rh-FSH) in human granulosa cells from patients undergoing in vitro fertilization.

DESIGN

Basic science research with a preclinical allosteric FSHR agonist.

SETTING

University hospital.

PATIENT(S)

Patients with infertility at a single academic fertility clinic were recruited under an Institutional Review Board-approved protocol. Primary granulosa cell cultures were established for 41 patients, of whom 8 had normal ovarian reserve (NOR), 17 were of advanced reproductive age (ARA), 12 had a diagnosis of polycystic ovary syndrome (PCOS), and 4 had a combination of diagnoses, such as ARA and PCOS.

INTERVENTION(S)

Primary granulosa-lutein (GL) cell cultures were treated with rh-FSH, TOP5300, or vehicle.

MAIN OUTCOME MEASURE(S)

Estradiol (E2) production using enzyme-linked immunosorbent assay, steroid pathway gene expression of StAR and aromatase using quantitative polymerase chain reaction, and FSHR membrane localization using immunofluorescence were measured in human GL cells.

RESULT(S)

TOP5300 consistently stimulated E2 production among patients with NOR, ARA, and PCOS. Recombinant FSH was the more potent ligand in GL cells from patients with NOR but was ineffective in cells from patients with ARA or PCOS. The lowest level of FSHR plasma membrane localization was seen in patients with ARA, although FSHR localization was more abundant in cells from patients with PCOS; the highest levels were present in cells from patients with NOR. The localization of FSHR was not affected by TOP5300 relative to rh-FSH in any patient group. TOP5300 stimulated greater expression of StAR and CYP19A1 across cells from all patients with NOR, ARA, and PCOS combined, although rh-FSH was unable to stimulate StAR and aromatase (CYP19A1) expression in cells from patients with PCOS. TOP5300-induced expression of StAR and CYP19A1 mRNA among patients with ARA and NOR was consistently lower than that observed in cells from patients with PCOS.

CONCLUSION(S)

TOP5300 appears to stimulate E2 production and steroidogenic gene expression from GL cells more than rh-FSH in PCOS, relative to patients with ARA and NOR. It does not appear that localization of FSHR at cell membranes is a limiting step for TOP5300 or rh-FSH stimulation of steroidogenic gene expression and E2 production.

Economic Evaluation of Medically Assisted Reproduction: A Methodological Systematic Review

BACKGROUND

Medically assisted reproduction (MAR) is a challenging application area for health economic evaluations, entailing a broad range of costs and outcomes, stretching out long-term and accruing to several parties.

PURPOSE

To systematically review which costs and outcomes are included in published economic evaluations of MAR and to compare these with health technology assessment (HTA) prescriptions about which cost and outcomes should be considered for different evaluation objectives.

DATA SOURCES

HTA guidelines and systematic searches of PubMed Central, Embase, WOS CC, CINAHL, Cochrane (CENTRAL), HTA, and NHS EED.

STUDY SELECTION

All economic evaluations of MAR published from 2010 to 2022.

DATA EXTRACTION

A predetermined data collection form summarized study characteristics. Essential costs and outcomes of MAR were listed based on HTA and treatment guidelines for different evaluation objectives. For each study, included costs and outcomes were reviewed.

DATA SYNTHESIS

The review identified 93 cost-effectiveness estimates, of which 57% were expressed as cost-per-(healthy)-live-birth, 19% as cost-per-pregnancy, and 47% adopted a clinic perspective. Few adopted societal perspectives and only 2% used quality-adjusted life-years (QALYs). Broader evaluations omitted various relevant costs and outcomes related to MAR. There are several cost and outcome categories for which available HTA guidelines do not provide conclusive directions regarding inclusion or exclusion.

LIMITATIONS

Studies published before 2010 and of interventions not clearly labeled as MAR were excluded. We focus on methods rather than which MAR treatments are cost-effective.

CONCLUSIONS

Economic evaluations of MAR typically calculate a short-term cost-per-live-birth from a clinic perspective. Broader analyses, using cost-per-QALY or BCRs from societal perspectives, considering the full scope of reproduction-related costs and outcomes, are scarce and often incomplete. We provide a summary of costs and outcomes for future research guidance and identify areas requiring HTA methodological development.

HIGHLIGHTS

The cost-effectiveness of MAR procedures can be exceptionally complex to estimate as there is a broad range of costs and outcomes involved, in principle stretching out over multiple generations and over many stakeholders.We list 21 key areas of costs and outcomes of MAR. Which of these needs to be accounted for alters for different evaluation objectives (determined by the type of economic evaluation, time horizon considered, and perspective).Published studies mostly investigate cost-effectiveness in the very short-term, from a clinic perspective, expressed as cost-per-live-birth. There is a lack of comprehensive economic evaluations that adopt a broader perspective with a longer time horizon. The broader the evaluation objective, the more relevant costs and outcomes were excluded.For several costs and outcomes, particularly those relevant for broader, societal evaluations of MAR, the inclusion or exclusion is theoretically ambiguous, and HTA guidelines do not offer sufficient guidance.

Pregnancy outcomes of intrauterine insemination without ovarian stimulation in couples affected by unilateral tubal occlusion and male infertility

BACKGROUND

Information available to date regarding the pregnancy outcomes of intrauterine insemination (IUI) without ovarian stimulation (OS) in infertile patients with unilateral tubal occlusion remains scarce. The objectives of this study were to investigate for couples affected by unilateral tubal occlusion (diagnosed via hysterosalpingography (HSG)/transvaginal real-time three-dimensional hysterosalpingo-contrast sonography (TVS RT-3D-HyCoSy)) and male infertility: (1) whether significant differences exist in pregnancy outcomes between IUI with or without OS cycles, and (2) whether the pregnancy outcomes of IUI without OS in women with unilateral tubal occlusion were similar to those of women with bilateral patent tubes.

METHODS

258 couples affected by male infertility completed 399 IUI cycles. The cycles were divided into three groups: group A, IUI without OS in women with unilateral tubal occlusion; group B, IUI with OS in women with unilateral tubal occlusion; and group C, IUI without OS in women with bilateral patent tubes. The main outcome measures, including clinical pregnancy rate (CPR), live birth rate (LBR), and first trimester miscarriage rate, were compared between either groups A and B or groups A and C.

RESULTS

Although the number of dominant follicles > 16 mm were significantly higher in group B than that in group A (group B vs. group A: 1.6 ± 0.6 vs. 1.0 ± 0.2, P < 0.001), the CPR, LBR, and first trimester miscarriage rate were comparable between these two groups. When comparing group C to group A, the duration of infertility was significantly longer in group C than that in group A (group A vs. group C: 2.3 ± 1.2 (year) vs. 2.9 ± 2.1 (year), P = 0.017). Except for the first trimester miscarriage rate, which was significantly higher in group A (42.9%, 3/7) than that in group C (7.1%, 2/28) (P = 0.044), no significant differences were observed in the CPR and LBR in these two groups. After adjusting for female age, body mass index, and the duration of infertility, similar results were obtained between groups A and C.

CONCLUSIONS

In couples affected by unilateral tubal occlusion (diagnosed via HSG/TVS RT-3D-HyCoSy) and male infertility, IUI without OS might be an alternative treatment strategy. However, when compared to patients with bilateral patent tubes, the patients with unilateral tubal occlusion showed a higher first trimester miscarriage rate following IUI without OS cycles. Further studies are warranted to clarify this relationship.

Expectant management versus IUI in unexplained subfertility and a poor pregnancy prognosis (EXIUI study): a randomized controlled trial

STUDY QUESTION

For couples with unexplained subfertility and a poor prognosis for natural conception, is 6 months expectant management (EM) inferior to IUI with ovarian stimulation (IUI-OS), in terms of live births?

SUMMARY ANSWER

In couples with unexplained subfertility and a poor prognosis for natural conception, 6 months of EM is inferior compared to IUI-OS in terms of live births.

WHAT IS KNOWN ALREADY

Couples with unexplained subfertility and a poor prognosis are often treated with IUI-OS. In couples with unexplained subfertility and a relatively good prognosis for natural conception (>30% in 12 months), IUI-OS does not increase the live birth rate as compared to 6 months of EM. However, in couples with a poor prognosis for natural conception (<30% in 12 months), the effectiveness of IUI-OS is uncertain.

STUDY DESIGN, SIZE, DURATION

We performed a non-inferiority multicentre randomized controlled trial within the infrastructure of the Dutch Consortium for Healthcare Evaluation and Research in Obstetrics and Gynaecology. We intended to include 1091 couples within 3 years. The couples were allocated in a 1:1 ratio to 6 months EM or 6 months IUI-OS with either clomiphene citrate or gonadotrophins.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We studied heterosexual couples with unexplained subfertility and a poor prognosis for natural conception (<30% in 12 months). The primary outcome was ongoing pregnancy leading to a live birth. Non-inferiority would be shown if the lower limit of the one-sided 90% risk difference (RD) CI was less than minus 7% compared to an expected live birth rate of 30% following IUI-OS. We calculated RD, relative risks (RRs) with 90% CI and a corresponding hazard rate for live birth over time based on intention-to-treat and per-protocol (PP) analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Between October 2016 and September 2020, we allocated 92 couples to EM and 86 to IUI-OS. The trial was halted pre-maturely owing to slow inclusion. Mean female age was 34 years, median duration of subfertility was 21 months. Couples allocated to EM had a lower live birth rate than couples allocated to IUI-OS (12/92 (13%) in the EM group versus 28/86 (33%) in the IUI-OS group; RR 0.40 90% CI 0.24 to 0.67). This corresponds to an absolute RD of minus 20%; 90% CI: -30% to -9%. The hazard ratio for live birth over time was 0.36 (95% CI 0.18 to 0.70). In the PP analysis, live births rates were 8 of 70 women (11%) in the EM group versus 26 of 73 women (36%) in the IUI-OS group (RR 0.32, 90% CI 0.18 to 0.59; RD -24%, 90% CI -36% to -13%) in line with inferiority of EM.

LIMITATIONS, REASONS FOR CAUTION

Our trial did not reach the planned sample size, therefore the results are limited by the number of participants.

WIDER IMPLICATIONS OF THE FINDINGS

This study confirms the results of a previous trial that in couples with unexplained subfertility and a poor prognosis for natural conception, EM is inferior to IUI-OS.

STUDY FUNDING/COMPETING INTEREST(S)

The trial was supported by a grant of the SEENEZ healthcare initiative. The subsidizing parties were The Dutch Organisation for Health Research and Development (ZonMW 837004023, www.zonmw.nl) and the umbrella organization of 10 health insurers in The Netherlands. E.R.G. receives personal fees from Titus Health care outside the submitted work. M.G. declares unrestricted research and educational grants from Guerbet, Merck and Ferring not related to the presented work, paid to their institution VU medical centre. A.B.H. reports receiving travel and speakers fees from Nordic Pharma and Merck and he is member of the Nordic Pharma ANGEL group and of the Safety Monitoring Board of Womed. C.B.L. reports speakers fee from Inmed and Yingming, and his department receives research grants from Ferring, Merck and Guerbet paid to VU medical centre. B.W.J.M. is supported by a NHMRC Investigator grant (GNT1176437) and reports consultancy for ObsEva and Merck. M.v.W. received a grant from the Netherlands Organisation for Health Research and Development ZonMW (80-8520098-91072). F.M. received two grants from the Netherlands Organisation for Health Research and Development ZonMW (NTR 5599 and NTR 6590). The other authors report no competing interest.

TRIAL REGISTRATION NUMBER

Dutch Trial register NL5455 (NTR5599).

TRIAL REGISTRATION DATE

18 December 2015.

DATE OF FIRST PATIENT’S ENROLMENT

26 January 2017.

The (decision) tree of fertility: an innovative decision-making algorithm in assisted reproduction technique

PURPOSE

Several mathematical models have been developed to estimate individualized chances of assisted reproduction techniques (ART) success, although with limited clinical application. Our study aimed to develop a decisional algorithm able to predict pregnancy and live birth rates after controlled ovarian stimulation (COS) phase, helping the physician to decide whether to perform oocytes pick-up continuing the ongoing ART path.

METHODS

A single-center retrospective analysis of real-world data was carried out including all fresh ART cycles performed in 1998-2020. Baseline characteristics, ART parameters and biochemical/clinical pregnancies and live birth rates were collected. A seven-steps systematic approach for model development, combining linear regression analyses and decision trees (DT), was applied for biochemical, clinical pregnancy, and live birth rates.

RESULTS

Of fresh ART cycles, 12,275 were included. Linear regression analyses highlighted a relationship between number of ovarian follicles > 17 mm detected at ultrasound before pick-up (OF17), embryos number and fertilization rate, and biochemical and clinical pregnancy rates (p < 0.001), but not live birth rate. DT were created for biochemical pregnancy (statistical power-SP:80.8%), clinical pregnancy (SP:85.4%), and live birth (SP:87.2%). Thresholds for OF17 entered in all DT, while sperm motility entered the biochemical pregnancy's model, and female age entered the clinical pregnancy and live birth DT. In case of OF17 < 3, the chance of conceiving was < 6% for all DT.

CONCLUSION

A systematic approach allows to identify OF17, female age, and sperm motility as pre-retrieval predictors of ART outcome, possibly reducing the socio-economic burden of ART failure, allowing the clinician to perform or not the oocytes pick-up.

OUP accepted manuscript

BACKGROUND

Intrauterine insemination with ovarian stimulation (IUI-OS) is a first-line treatment for unexplained infertility. Gonadotrophins, letrozole and clomiphene citrate (CC) are commonly used agents during IUI-OS and have been compared in multiple aggregate data meta-analyses, with substantial heterogeneity and no analysis on time-to-event outcomes. Individual participant data meta-analysis (IPD-MA) is considered the gold standard for evidence synthesis as it can offset inadequate reporting of individual studies by obtaining the IPD, and allows analyses on treatment–covariate interactions to identify couples who benefit most from a particular treatment.

OBJECTIVE AND RATIONALE

We performed this IPD-MA to compare the effectiveness and safety of ovarian stimulation with gonadotrophins, letrozole and CC and to explore treatment–covariate interactions for important baseline characteristics in couples undergoing IUI.

SEARCH METHODS

We searched electronic databases including MEDLINE, EMBASE, CENTRAL, CINAHL, and PsycINFO from their inception to 28 June 2021. We included randomized controlled trials (RCTs) comparing IUI-OS with gonadotrophins, letrozole and CC among couples with unexplained infertility. We contacted the authors of eligible RCTs to share the IPD and established the IUI IPD-MA Collaboration. The primary effectiveness outcome was live birth and the primary safety outcome was multiple pregnancy. Secondary outcomes were other reproductive outcomes, including time to conception leading to live birth. We performed a one-stage random effects IPD-MA.

OUTCOMES

Seven of 22 (31.8%) eligible RCTs provided IPD of 2495 couples (62.4% of the 3997 couples participating in 22 RCTs), of which 2411 had unexplained infertility and were included in this IPD-MA. Six RCTs (n = 1511) compared gonadotrophins with CC, and one (n = 900) compared gonadotrophins, letrozole and CC. Moderate-certainty evidence showed that gonadotrophins increased the live birth rate compared to CC (6 RCTs, 2058 women, RR 1.30, 95% CI 1.12–1.51, I² = 26%). Low-certainty evidence showed that gonadotrophins may also increase the multiple pregnancy rate compared to CC (6 RCTs, 2058 women, RR 2.17, 95% CI 1.33–3.54, I² = 69%). Heterogeneity on multiple pregnancy could be explained by differences in gonadotrophin starting dose and choice of cancellation criteria. Post-hoc sensitivity analysis on RCTs with a low starting dose of gonadotrophins (≤75 IU) confirmed increased live birth rates compared to CC (5 RCTs, 1457 women, RR 1.26, 95% CI 1.05–1.51), but analysis on only RCTs with stricter cancellation criteria showed inconclusive evidence on live birth (4 RCTs, 1238 women, RR 1.15, 95% CI 0.94–1.41). For multiple pregnancy, both sensitivity analyses showed inconclusive findings between gonadotrophins and CC (RR 0.94, 95% CI 0.45–1.96; RR 0.81, 95% CI 0.32–2.03, respectively). Moderate certainty evidence showed that gonadotrophins reduced the time to conception leading to a live birth when compared to CC (6 RCTs, 2058 women, HR 1.37, 95% CI 1.15–1.63, I² = 22%). No strong evidence on the treatment–covariate (female age, BMI or primary versus secondary infertility) interactions was found.

WIDER IMPLICATIONS

In couples with unexplained infertility undergoing IUI-OS, gonadotrophins increased the chance of a live birth and reduced the time to conception compared to CC, at the cost of a higher multiple pregnancy rate, when not differentiating strategies on cancellation criteria or the starting dose. The treatment effects did not seem to differ in women of different age, BMI or primary versus secondary infertility. In a modern practice where a lower starting dose and stricter cancellation criteria are in place, effectiveness and safety of different agents seem both acceptable, and therefore intervention availability, cost and patients’ preferences should factor in the clinical decision-making. As the evidence for comparisons to letrozole is based on one RCT providing IPD, further RCTs comparing letrozole and other interventions for unexplained infertility are needed.