The impact of Duostim protocol on pregnancy outcomes in infertile patients: A meta-analysis comparing single and double conventional stimulation cycles

Abstract

Background

The DuoStim protocol has been proposed as an alternative to conventional single and double stimulation cycles in the treatment of infertility. However, its efficacy in improving pregnancy outcomes remains uncertain.

Objective

To systematically evaluate the impact of the DuoStim protocol on pregnancy outcomes in infertile patients by comparing it with single and double conventional stimulation cycles.

Methods

An online systematic search was conducted using PubMed, Cochrane Library, and EMBASE databases, covering the period from their inception to March 2024. Randomized controlled trials (RCTs) comparing the DuoStim protocol with single and double conventional stimulation cycles in infertile patients were identified. Data were extracted by two independent investigators who screened the literature and assessed the quality of the studies. Meta-analysis was performed using RevMan 5.4 software.

Results

A total of six RCTs involving 414 infertile patients were included. The DuoStim protocol significantly increased the total number of oocytes compared to single and double conventional stimulation (MD =  − 1.47; 95% CI, − 2.12 to − 0.82; P < 0.00001). There were no statistically significant differences in the number of MII oocytes, total embryos, pregnancy rate, and live birth rate. Subgroup Analysis: compared to single stimulation, the DuoStim protocol significantly increased the number of MII oocytes (MD = 1.71; 95% CI, 0.77 to 2.66; P = 0.0004) and total embryos (MD = 1.34; 95% CI, 0.61 to 2.08; P = 0.0003). There were no significant differences in pregnancy rate and live birth rate. Secondary outcomes showed the effect of the DuoStim protocol in patients undergoing preimplantation genetic testing for aneuploidies (PGT-A). The time to obtain euploid blastocysts was significantly reduced in the DuoStim group compared to the control group (23.3 ± 2.8 days vs. 44.1 ± 2.0 days; P < 0.001).

Conclusions

The DuoStim protocol shows a significant advantage in increasing the total number of oocytes, MII oocytes, and embryos compared to single stimulation. However, it does not significantly improve pregnancy and live birth rates. The protocol also shortens the time to obtain euploid blastocysts in patients undergoing PGT-A, indicating potential benefits for specific patient groups. Further research is needed to confirm these findings and evaluate long-term outcomes. Thus, the quality of evidence should be considered moderate, warranting cautious interpretation of the results.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10815-024-03304-5.

Introduction

Infertility is a significant and growing health issue, affecting up to 16% of couples worldwide [1]. To address this problem, assisted reproductive technology (ART) utilizes controlled ovarian stimulation (COS) to promote the growth and maturation of multiple follicles through hormonal treatment, aiding infertile women in achieving pregnancy. Despite advances in ART, traditional COS protocols may be less effective for certain patients, particularly those with diminished ovarian reserve, who may benefit from tailored approaches [2].

Age and the number of oocytes retrieved during in vitro fertilization (IVF) treatment are well-documented factors influencing clinical outcomes and are considered independent predictors of pregnancy success [3, 4]. Research suggests that, according to the POSEIDON criteria, each additional oocyte retrieved can significantly increase live birth rates in patients with poor reproductive prognosis, particularly those of advanced reproductive age [5].

Recent developments in stimulation protocols, such as DuoStim, are based on the concept of follicular waves, defined as the synchronous growth of a cohort of follicles at regular intervals throughout the menstrual cycle [6]. DuoStim involves two stimulation cycles (follicular phase stimulation and luteal phase stimulation) within a single menstrual cycle, aiming to maximize the number of oocytes retrieved and improving pregnancy rates [7]. In contrast, conventional COS protocols typically involve only one stimulation and one oocyte retrieval per menstrual cycle [8].

Several studies suggest that DuoStim may increase the number of oocytes retrieved and, consequently, improve pregnancy outcomes and live birth rates in patients with poor ovarian response [9]. However, the mandatory freezing and thawing processes in DuoStim could pose risks, including oocyte and embryo wastage. Meta-analyses have shown that DuoStim is associated with a higher number of oocytes retrieved, mature MII oocytes, and high-quality embryos compared to conventional stimulation [10]. However, many of these studies were not randomized controlled trials (RCTs), which may limit the strength of the evidence.

A more recent meta-analysis [11], including both randomized and non-randomized controlled trials, compared the outcomes of luteal phase initiation of ovarian stimulation (DuoStim) with conventional COS protocols. This study found that pregnancy outcomes in patients with poor ovarian response were similar between DuoStim and conventional protocols, though DuoStim may offer logistical advantages, such as a shorter overall treatment timeframe [9].

Given the limitations and variability in the quality of evidence from previous studies, a comprehensive systematic meta-analysis is needed to summarize the available data and provide a more definitive evaluation of DuoStim’s effectiveness [10, 11]. This meta-analysis focuses on comparing DuoStim with single and double conventional stimulation cycles in infertile patients, with the goal of assessing clinical pregnancy rates, embryo implantation rates, and live birth rates to provide evidence-based recommendations for clinical practice.

Methods

We conducted a systematic online search using PubMed, Cochrane Library, EMBASE, and ClinicalTrials.gov databases, covering the period from their inception to March 2024. To ensure methodological rigor, we conducted the review and meta-analysis according to the Cochrane Handbook for Systematic Reviews of Interventions and reported our findings following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [12, 13]. This review and meta-analysis were registered with PROSPERO, registration number CRD42024522779.

Criteria for including studies

Types of research

Randomized controlled trials on DuoStim stimulation and conventional stimulation protocols in infertile patients, with no restriction on publication date. DuoStim is defined as a protocol that involves simultaneous follicular phase stimulation (early in the menstrual cycle) and luteal phase stimulation (later in the same cycle). This study compares the DuoStim protocol with conventional stimulation conducted during the follicular or luteal phase alone, or simultaneous comparisons with conventional stimulation carried out in different cycles, which does not constitute a single DuoStim cycle.

Study participants

Patients undergoing controlled ovarian stimulation cycles, particularly those with poor prognosis or diminished ovarian reserve. Poor prognosis based on the definitions in the included studies as patients with low oocyte yield and decreased ovarian reserve according to the POSEIDON criteria. Poor response is defined as AMH < 1.5 ng/mL, AFC < 5, or ≤ 5 oocytes retrieved in previous stimulation cycles.

Exclusion criteria

1. Untreated autoimmune, endocrine, or metabolic diseases, or a history of ovarian cystectomy or oophorectomy.

2. Studies with incomplete or missing data.

3. Duplicate publications (the study with the most comprehensive data will be selected).

4. Studies that only compare follicular phase and luteal phase stimulation within the DuoStim framework.

5. Women whose male partners require sperm retrieval through testicular extraction.

Interventions

Experimental Group: Given the DuoStim stimulation protocol.

DuoStim is defined as conducting both follicular phase stimulation (early in the menstrual cycle) and luteal phase stimulation (later in the same cycle) within the same menstrual cycle.

Control Group: Given one or two conventional stimulation protocols.

Single Conventional Stimulation: Ovarian stimulation is performed within one cycle, followed by either a fresh embryo transfer or a frozen-thawed embryo transfer.

Double Conventional Stimulation: After the first stimulation, a second stimulation is performed in the next cycle. Any surplus embryos are cryopreserved and transferred at an appropriate time to increase overall pregnancy success rates.

Outcome measures

In this study, the primary outcome indicators include the total number of oocytes, the number of mature oocytes, the total number of embryos, the pregnancy rate, and the live birth rate. Secondary outcome indicators include the euploid embryo rate and the time required to obtain euploid embryos. We primarily focused on pregnancy outcomes for each stimulation cycle up to the point of live birth. To provide a more comprehensive evaluation of pregnancy outcomes, some studies reported cumulative pregnancy rates based on tracking patients across multiple cycles.

Search strategy

We used a combination of keywords and subject headings in our search, including DuoStim, Double Stimulat*, Fertilization in Vitro, Sperm Injections, Intracytoplasmic, Embryo Transfer, and Reproductive Techniques. To avoid missing potentially relevant studies, no restrictions were placed on publication date or status (see Supplementary Table 1). A detailed description of the search strategy can be found at https://www.crd.york.ac.uk/PROSPEROFILES/522779_STRATEGY_20240310.pdf.

Evaluation of literature quality and data extraction

Two researchers independently screened the retrieved literature and compared the screening results. If there were any discrepancies, a third researcher was consulted to decide whether to include the literature. Extracted data included the first author’s name, publication date, patient characteristics, interventions, control measures, and outcome indicators. We also searched for the necessary data in the ClinicalTrials.gov databases using the registration numbers provided in the articles. The methodological quality of the included studies was assessed using the risk of bias assessment tool from the Cochrane Handbook for Systematic Reviews of Interventions (RevMan 5.4).

Risk of bias assessment

The risk of bias assessment for the included studies was conducted using the tool recommended by the Cochrane Handbook for Systematic Reviews of Interventions [14]. The assessment criteria were as follows: (1) whether the randomization method was correct; (2) whether the allocation was concealed; (3) whether blinding was used for participants and researchers; (4) the completeness of outcome data; (5) whether there was selective reporting of study results; and (6) other sources of bias. The risk of bias was independently assessed by two reviewers, and any discrepancies were discussed and resolved.

Statistical analysis

Meta-analysis was performed using RevMan 5.4 statistical software. For continuous outcome variables, the effect size is represented as the mean difference (MD) with a 95% confidence interval (CI). For dichotomous outcome variables, the effect size is represented as the relative risk (RR) with a 95% confidence interval (CI). Due to the limited number of included studies, secondary outcome indicators were not fully described. Subgroup analyses will be conducted for the control group comparing single conventional stimulation and double conventional stimulation, followed by a combined analysis. Single Conventional Stimulation: Ovarian stimulation is performed within one cycle, followed by either a fresh embryo transfer or a frozen-thawed embryo transfer. Double Conventional Stimulation: After the first stimulation, a second stimulation is performed in the next cycle. Any surplus embryos are cryopreserved and transferred at an appropriate time to increase overall pregnancy success rates. The relationship between the two groups will be statistically analyzed using the chi-square test. Significant heterogeneity among the included studies is determined by a P-value < 0.1 and I² > 50%. The meta-analysis will use a random effects model for heterogeneity testing. Since fewer than 10 studies were included, publication bias was not assessed.

Results

Search results

We identified 817 articles. After removing duplicates, 161 articles remained. By reviewing abstracts and titles, 637 articles were excluded. Finally, after reading the full texts, 6 RCTs were included, encompassing a total of 414 patients [15–20]. The literature screening process and results are shown in Fig. 1.

Fig. 1.

Flowchart of included studies

General characteristics of the included studies

The sample sizes of the infertility patients ranged from 42 to 107, with 208 participants randomly assigned to the treatment group and 206 participants randomly assigned to the control group. The ages of the patients were between 25 and 40 years, primarily consisting of patients with poor ovarian reserve, poor ovarian response, and poor prognosis. Five studies reported on DuoStim and single stimulation [15, 17–20], and two studies reported on DuoStim and double stimulation [16, 18]. The characteristics of the included studies are listed in Table 1.

Table 1.

Characteristics of included studies

Study	Country	study design	Patient characteristics	Age	Participants	Transplant type	Interventions	Overall	size	Comparator	Size	Outcome
Saharkhiz, 2024 [20]	Iran	RCT	POR	≥ 35 years	antral follicle count (AFC) level < 5, and anti-Mullerian hormone (AMH) level < 1.2 ng/ml), A total of 42 women	None	DuoStim protocol	42	21	Minimal stimulation protocol	21	MII oocytes、Total embryos、Total embryos
Racca, 2023 [19]	Denmark	RCT	POR	< 40 years old)	poor-prognosis (AMH < 1.2 ng/mL) patients	ET and FET	Duostim fresh	107	53	Single stimulation cycle	53	MII oocytes
Massin, 2023   [18]	France	RCT	POR	UNKNOWN	AFC ≤ 5 and/or AMH ≤ 1.2 ng/ml and ≤ 3 oocytes if previous IVF	ET and FET	Duostim group	88	44	Two consecutive antagonist cycles	44	Total oocytes、MII oocytes、Total embryos、Pregnancy rate、Live birth rate
Fatemeh Ghahghayi, 2024 [17]	Iran	RCT	POR	35 ± 4	(AMH) ≤ 1.2 ng/ml, antral follice counts (AFC) ≤ 6 on the third day of the menstrual cycle	FET	DuoStim protocol	50	25	The conventional antagonist cycle	25	Total oocytes、 MII oocytes、Total embryos、Total embryos
Cerrillo,  2023 [16]	Spain	RCT	POR	≥ 38 years old	antiMüllerian hormone (AMH) < 1.2 ng/ ml, Antral Follicular Count (AFC) < 5, and previous ovarian response of < 4 or 4–9 eggs retrieved	FET	DuoStim group	80	41	Two ovarian stimulations	39	Total oocytes、MII oocytes、Time to euploid embryo (days)、euploid embryos、Total embryos、Pregnancy rate、Live birth rate
Boudry, 2024  [15]	Belgium	RCT	POR	aged 25–40	(AMH) level of ≤ 1.5 ng/mL, antral follicle count (AFC) of 6, or 5 oocytes after a previous stimulation	FET	DuoStim group	48	24	Ovarian stimulation	24	Total oocytes、MII oocytes、Pregnancy rate、Live birth rate

Risk of bias assessment

Among the included studies, two studies used computer-generated random allocation [18, 20], one study employed convenient non-probability sampling methods [17] and three studies mentioned randomization without specific descriptions [15, 16, 19]. Allocation concealment was performed by doctors in two studies [17, 18], by a third party in one study [20], and not mentioned in three studies [15, 16, 19]. Blinding was conducted for participants, trial personnel, and researchers in three studies [16, 19, 20], while two studies did not describe blinding [17, 19], and one study explicitly stated no blinding [18]. None of the included studies exhibited selective reporting bias, and data integrity was well maintained (Fig. 2).

Fig. 2.

Risk of bias graph: authors’ guide of each risk of bias item presented as

percentages across all included studies.

Meta-analysis results

Total oocytes

This study included four RCTs [15–18], with a total of 306 cases. The random-effects model analysis showed that the DuoStim protocol was significantly superior to both single and double conventional stimulation protocols in increasing the total number of oocytes, with high heterogeneity (MD =  − 1.47, 95% CI, − 2.12, − 0.82, P < 0.00001). Subgroup analysis indicated that, based on the analysis of two RCTs [15, 17], there was no significant difference in the total number of oocytes between the DuoStim protocol and the single conventional stimulation protocol (MD = 0.47; 95% CI, − 0.59–1.53, P = 0.39). In contrast, the analysis of two other RCTs [16, 18] showed that the DuoStim protocol yielded significantly more oocytes compared to the double conventional stimulation protocol (MD =  − 2.65; 95% CI, − 3.47 to − 1.82, P < 0.00001) (Fig. 3).

Fig. 3.

Comparison of total oocytes between DuoStim and conventional stimulation cycles

Number of MII oocytes

This study included six RCTs [15–20], with a total of 414 cases. The random-effects model analysis showed that the DuoStim protocol did not exhibit a significant advantage in the number of MII oocytes (MD = 0.99; 95% CI, − 0.53–2.51, P = 0.20). Subgroup analysis indicated that, based on the analysis of five RCTs [15, 17, 18, 20, 19], the DuoStim protocol significantly increased the number of MII oocytes compared to a single stimulation cycle (MD = 1.71; 95% CI, 0.77–2.66, P = 0.0004). In contrast, the analysis of two RCTs [16, 18] showed that there was no significant difference in the number of MII oocytes between the DuoStim protocol and two conventional stimulation cycles (MD =  − 0.65; 95% CI, − 3.20–1.89, P = 0.61) (Fig. 4).

Fig. 4.

Comparison of MII oocytes between DuoStim and conventional stimulation cycles

Total number of embryos

This study included a total of four RCTs [16–18, 20], comprising 256 cases. The results of the random-effects model analysis showed that the DuoStim scheme did not exhibit a significant advantage over the conventional stimulation scheme in increasing the total number of embryos, and the heterogeneity was high (MD =  − 0.50; 95% CI, − 3.22–2.22, P = 0.72). The analysis of two RCTs [17, 20] indicated that the DuoStim scheme demonstrated a significant advantage in increasing the total number of embryos compared to a single stimulation cycle (MD = 1.34; 95% CI, 0.61–2.08, P = 0.0003). The analysis of two RCTs [16, 18] showed that there was no significant difference in the total number of embryos when comparing the DuoStim scheme to two conventional stimulation cycles (MD =  − 2.45; 95% CI, − 5.88–0.89, P = 0.16). (Fig. 5).

Fig. 5.

Comparison of total embryos between DuoStim and conventional stimulation cycles

Pregnancy rate

This study included three RCTs [15, 16, 18], comprising a total of 214 cases. The random-effects model analysis showed no statistically significant difference in pregnancy rates between the DuoStim protocol and conventional stimulation protocols (RR = 0.97; 95% CI, 0.41–2.31, P = 0.95). Subgroup analysis indicated that the analysis of one RCT [15] showed no significant difference in pregnancy rates when comparing the DuoStim protocol with a single stimulation cycle (RR = 2.00; 95% CI, 0.91–4.41, P = 0.09). Additionally, the analysis of two RCTs [16, 18] showed no significant difference in pregnancy rates between the DuoStim protocol and two conventional stimulation cycles (RR = 0.68; 95% CI, 0.29 – 1.61, P = 0.38) (Fig. 6).

Fig. 6.

Comparison of pregnancy rates between DuoStim and conventional stimulation cycles

Live birth rate

This study included three RCTs [15, 16, 18], comprising a total of 206 cases. The random-effects model analysis showed no statistically significant difference in live birth rates between the DuoStim protocol and conventional stimulation protocols (RR = 1.31; 95% CI, 0.81–2.12, P = 0.26). Subgroup analysis indicated that the analysis of one RCT [15] showed no significant difference in live birth rates when comparing the DuoStim protocol with a single stimulation cycle (MD = 1.33; 95% CI, 0.55–3.24, P = 0.52). Additionally, the analysis of two RCTs [16, 18] showed no significant difference in live birth rates between the DuoStim protocol and two conventional stimulation cycles (RR = 1.31; 95% CI, 0.74–2.31, P = 0.35) (Fig. 7).

Fig. 7.

Comparison of live birth rates between DuoStim and conventional stimulation cycles

Secondary outcomes

A study investigated [16] the efficacy of the DuoStim strategy in replacing conventional two-cycle ovarian stimulation for poor prognosis patients undergoing preimplantation genetic testing for aneuploidy (PGT-A), aiming to increase euploidy rates and reduce the time to obtain the first euploid embryo. It assessed the time required to obtain a euploid embryo and the primary cycle outcomes. Results indicated a euploidy rate of 39.0% per patient in the control group and 45.7% in the DuoStim group. Notably, the DuoStim group showed a significantly shorter average time to obtain a euploid blastocyst (23.3 ± 2.8 days) compared to the control group (44.1 ± 2.0 days, P < 0.001). The study concluded that the DuoStim strategy for poor prognosis patients undergoing PGT-A cycles can maintain comparable euploidy rates while significantly reducing the time needed to obtain a euploid blastocyst.

Discussion

Our analysis found that the DuoStim protocol significantly outperformed both single and double conventional stimulation protocols in terms of total oocyte count. Compared to a single stimulation cycle, DuoStim also showed significant advantages in the number of mature (MII) oocytes and total embryos. However, it did not demonstrate a significant advantage in improving pregnancy rates and live birth rates.

Studies have shown [6, 7] that multiple follicular waves may occur within a single ovarian cycle. Based on this theory, patients with poor ovarian function, poor prognosis, or low ovarian response can obtain more oocytes through unconventional stimulation protocols. Specifically, this theory posits that the dynamic growth of follicles does not cease, thereby allowing for the consecutive recruitment of 2–3 cohorts of antral follicles within a single ovarian cycle. The DuoStim protocol combines luteal phase stimulation (LPS) and follicular phase stimulation (FPS) within the same ovarian cycle, resulting in two stimulation rounds in one menstrual cycle.

Follicular phase stimulation (FPS) begins after the selection of a dominant follicle or immediately before ovulation while maintaining fertility. Luteal phase stimulation (LPS) involves administering gonadotropins between days 17 and 21 of the cycle. This strategy has been recommended for patients with diminished ovarian reserve or those whose previous cycles were canceled due to non-response. FPS and LPS are considered to exhibit the same clinical, obstetric, and perinatal outcomes [21]. The DuoStim protocol, by implementing two stimulations within one cycle, may more effectively utilize ovarian reserves, thereby increasing the chances of obtaining more oocytes. This approach is particularly suitable for patients with poor ovarian reserve [22].

Studies have shown [22] that in women with insufficient ovarian reserve, adding luteal phase stimulation significantly increases the number of oocytes and transferable embryos per menstrual cycle compared to follicular stimulation alone, thereby enhancing pregnancy chances. Moreover, implementing luteal phase stimulation within the same cycle has proven to be an effective strategy to rescue poor responders who did not produce embryos after the first stimulation. The DuoStim protocol yields a similar number of oocytes compared to two conventional stimulations, demonstrating that DuoStim is an effective approach for patients with poor reproductive prognosis to obtain more oocytes.

Our results align with previous studies, showing that the DuoStim protocol significantly outperforms single and double conventional stimulation protocols in total oocyte count. This may be attributed to the two stimulations within one cycle, maximizing the utilization of ovarian reserves. In comparison to the number of mature oocytes (MII) and total embryos, the DuoStim protocol showed a significant advantage over single conventional stimulation, but no significant difference compared to double conventional stimulation. This suggests that the DuoStim protocol may increase the number of mature oocytes by increasing the frequency of follicular stimulation, achieving a similar outcome to that of double conventional ovarian stimulation. Therefore, these findings support the DuoStim protocol as a viable option for urgent fertility preservation, providing a feasible choice for fertility preservation [23, 24].

Although the DuoStim protocol shows advantages in the number of retrieved oocytes and accumulated embryos, it does not improve pregnancy outcomes for patients with poor ovarian response (POR) [18]. While DuoStim fresh produces more blastocysts in young patients with low prognosis, it remains unclear whether it can improve embryo transfer rates and pregnancy outcomes, and the decision to undergo dual stimulation should be carefully evaluated. However, the results supporting an increase in cumulative live birth rates are well-founded [19].

Our study aligns with previous research, showing no significant difference in pregnancy rates and live birth rates between the DuoStim protocol and single or double conventional stimulation protocols. This suggests that although the DuoStim protocol increases the number of oocytes and embryos, these advantages do not necessarily translate into higher pregnancy rates. One possible reason is that the DuoStim protocol involves two stimulations within the same ovarian cycle. Oocytes and embryos from the first stimulation must be cryopreserved, with the option of fresh or thawed transfer only after the second retrieval. Despite continuous improvements in cryopreservation techniques, the vitrification process after the first stimulation can still cause lysis and loss of some embryos and oocytes. Therefore, DuoStim does not show a significant advantage in pregnancy or live birth rates. However, as the DuoStim protocol yields more oocytes and embryos, it offers more opportunities for transfer, potentially increasing the cumulative pregnancy rate. We acknowledge that a possible reason is that an increase in the number of embryos does not necessarily lead to higher delivery rates, which may be related to factors such as embryo quality, patient characteristics (e.g., age and health status), transfer strategy, and the risk of multiple pregnancies.

Studies have shown [25] that the high incidence of chromosomal aneuploidy in human gametes and embryos is a major cause of IVF miscarriages and failures. Factors such as aging, poor lifestyle habits, and environmental pollution can lead to chromosomal abnormalities in embryos. The application of PGT-A technology is crucial for improving live birth rates in older patients and those with poor prognosis [26]. During PGT-A treatment for AMA/POR women, using DuoStim after conventional stimulation can be recommended to rescue low blastocyst yields. It can indeed prevent mid-cycle dropout or further aging [27]. Utilizing the DuoStim strategy in poor prognosis patients undergoing PGT-A cycles maintains a similar euploidy rate while reducing the time needed to obtain euploid blastocysts [18]. DuoStim shortens the time to pregnancy, minimizes treatment interruptions, and may be cost-effective [16].

This study found that for patients with poor prognosis undergoing PGT-A cycles, the DuoStim strategy can maintain a comparable euploidy rate while significantly reducing the time required to obtain euploid blastocysts. The possible mechanism is that the DuoStim protocol, by administering two stimulations within one menstrual cycle, may more effectively utilize ovarian reserves. Preimplantation genetic testing for aneuploidy (PGT-A) reduces pregnancy time and miscarriage rates in certain cases, particularly for older patients with poor prognosis. Similar to older patients, poor responders and those with suboptimal reproductive status often need multiple ovarian stimulation cycles to accumulate sufficient oocytes and embryos. The DuoStim protocol offers an option for patients with poor reproductive prognosis, enabling them to obtain euploid embryos in a shorter time. The foundation of PGT-A technology is to select embryos with developmental potential from a sufficient number of embryos. The effective combination of the DuoStim protocol and PGT-A technology undoubtedly represents the optimal treatment choice for patients with poor prognosis and diminished ovarian reserve.

Studies have shown that the DuoStim strategy can achieve two oocyte retrievals within a single menstrual cycle, which is particularly important for cancer patients who require urgent fertility preservation [24, 28]. DuoStim allows for increased oocyte yield without delaying cancer treatment, thereby enhancing the effectiveness of fertility preservation [23, 24]. Moreover, luteal phase stimulation can be flexibly initiated immediately after the follicular phase stimulation without significantly impacting the quantity or quality of the oocytes [29]. This feature highlights the potential of DuoStim in non-conventional treatment approaches.

The combination of DuoStim with random-start stimulation is especially suitable for patients with diminished ovarian reserve or limited treatment windows. Random-start stimulation can be initiated at any time during the menstrual cycle, avoiding the need to wait for the onset of menstruation. This approach increases the flexibility of starting treatment and improves the overall feasibility of the treatment plan [22, 30]. By combining random-start with luteal phase stimulation, it is possible to obtain two batches of oocytes within a single cycle, thereby increasing the cumulative number of embryos and providing more options for subsequent treatment [18, 27].

In cancer patients, the modified DuoStim protocol allows for two consecutive ovarian stimulations within a short period without interfering with cancer treatment. This method not only increases the number of retrieved oocytes but also maximizes the utilization of the patient’s ovarian reserve [23, 24]. Research indicates that optimizing stimulation parameters in the follicular and luteal phases can effectively increase embryo formation rates and cumulative live birth rates while significantly reducing the overall treatment duration [31]. Therefore, DuoStim is particularly suitable for cancer patients who need to undergo oocyte cryopreservation within a limited timeframe.

Among the included studies, the randomization processes varied, with only two studies employing computer-generated random allocation, potentially leading to selection bias in other studies. Blinding was inconsistent across the studies, with three studies adequately performing blinding while two studies did not provide enough details, and one explicitly stated no blinding, increasing the risk of performance and detection biases. Despite these limitations, none of the studies demonstrated selective reporting bias, and data integrity was maintained. While the risk of bias was generally low in most categories, the lack of detailed descriptions in some studies lowers the confidence in the overall evidence. Thus, the quality of evidence should be considered moderate, warranting cautious interpretation of the results.

Finally, although the DuoStim protocol shows certain advantages in the number of oocytes and embryos, its effectiveness in improving pregnancy rates and live birth rates has not been fully substantiated. However, it has been shown to reduce the time required to obtain euploid blastocysts.

This meta-analysis has several limitations. First, the high heterogeneity among the included studies may affect the stability of the results. Second, the small sample sizes in some studies could lead to insufficient statistical power. Finally, variations in stimulation protocols and patient characteristics across different studies may influence the outcomes.

In conclusion, our findings demonstrate that the DuoStim protocol offers a distinct advantage in increasing the total number of oocytes, MII oocytes, and embryos compared to single stimulation cycles. However, this benefit does not extend to significantly improving pregnancy or live birth rates. Moreover, DuoStim reduces the time to obtain euploid blastocysts in patients undergoing PGT-A, indicating potential advantages for specific patient groups. Thus, the quality of evidence should be considered moderate, warranting cautious interpretation of the results. While these results are promising, further well-designed studies are required to confirm these findings and assess the long-term clinical outcomes associated with DuoStim.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contribution

Y. Z. contributed to conceptualization, methodology, and writing the original draft. W. L and Y. L. was responsible for data curation and formal analysis. B. L. handled investigation and visualization. L. Z. provided resources and supervision. Z. Y. managed software and validation. K. F. oversaw project administration and funding acquisition. D. L. contributed to reviewing and editing the manuscript. S. C. provided supervision and validation. X. L. contributed to conceptualization, supervision, project administration, and is the corresponding author. All authors have significantly contributed to this work and agree to be accountable for its content.

Data Availability

Our study has included all relevant data within the manuscript and supporting materials. If additional data is required for further verification, it is available from the corresponding author upon reasonable request.

Declarations

Conflict of interest

The authors declare no competing interests.