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The clinical value of short-term insemination: a retrospective analysis of 3496 patients

BMC Pregnancy and Childbirth volume 25, Article number: 30 (2025) Cite this article

Abstract

Background

The safety and effectiveness of short-term insemination remain a subject of controversy. This study aims to investigate the impact of short-term insemination on both embryo quality and pregnancy outcomes and whether it is necessary to apply short-term insemination to all patients underwent in vitro fertilization (IVF).

Methods

A retrospective analysis was conducted on 3,496 patients from two centers over the period January 2016 to December 2022. Of these, 1307 patients underwent IVF, 1656 patients were treated with short-term IVF, 166 patients received early rescue intracytoplasmic sperm injection (R-ICSI) and 367 patients were treated with ICSI. The clinical and neonatal outcomes were compared between the two groups.

Results

The rate of high-quality embryos was significantly lower in the short-term IVF group compared to the routine IVF group (59.89% vs. 68.16%) (P = 0.000), the rate of blastocyst formation was significantly lower in the short-term IVF group compared to the routine IVF group (44.99% vs. 61.34%) (P = 0.000). There were no significant differences in clinical outcomes or neonatal outcomes between the two groups, irrespective of whether fresh or frozen embryos were used (both P > 0.05). The incidence of ≥ 3PN demonstrated no significant difference between the early R-ICSI and ICSI groups (1.04% vs. 0.66%) (P = 0.114), furthermore, the clinical outcomes were similar in both groups, for both fresh and frozen embryos (both P > 0.05).

Conclusions

For patients with primary fertility, short-term IVF combined with early R-ICSI can effectively prevent potential low fertilization or fertilization failure, reduce the risk of patients with no transferable embryo, avoid the waste of resources and had no adverse effects on neonatal outcomes. However, short-term IVF reduced the oocytes utilization rate in one single oocyte pick-up cycle, for patients with no risk factors for fertilization failure, the overnight fertilization is still one of the most important ways of insemination worthy of affirmation.

Trial registration

NA.

Peer Review reports

Background

Human infertility, recognized as the third largest serious disease in the world, is progressively emerging as a major public concern on health [1], affects approximately one-sixth of couples and 186 million people worldwide [2]. Infertility results in serious social and health consequences, such as economic burden and deterioration in physical and mental health status [3]. Over the past four decades, assisted reproductive technology (ART) has rapidly developed, providing hope to people suffering from infertility [4]. How to improve embryo utilization and provide more pregnancy opportunities for infertile patients through in vitro fertilization embryo transfer (IVF-ET) is an important topic within the field of ART.

Fertilization is an important biological event marking the beginning of a new life [5]. Throughout the fertilization process, the fusion of sperm and mature oocytes forms a diploid zygote, and the presence of the second polar body and two pronuclei indicates successful fertilization [6]. Even with normospermia, about one-fifth of IVF patients experience a low fertilization rate, defined as below 25% [7], more dishearteningly, 5–10% of IVF cycles experience total fertilization failure (TFF) [8]. Despite improvements in IVF-ET technology, low fertilization rates and TFF remain common in traditional IVF. This is a major concern for clinicians, embryologists, and patients, as it can result in wasted oocytes and consequently a lack of transferable embryos [9]. Late rescue intracytoplasmic sperm injection (late R-ICSI) on the second day after IVF failure was first introduced in 1993 as a method to reduce the losses caused by TFF [10], however, its success rate was found to be low [11]. The underlying factors can be categorized into two primary aspects: firstly, the quality of oocytes decreases over time and secondly, the asynchronous growth of the endometrium and embryonic development [12]. Studies have shown that short-term IVF combined with early R-ICSI at 4–6 h after insemination could prevent oocyte aging and enhance fertilization outcomes [9, 13], however, there is also study showing that compared with the standard overnight gamete co-incubation, a shortened sperm-oocyte coincubation time had no beneficial effects on embryo quality [14]. Furthermore, to identify unfertilized oocytes and implement early ICSI, embryologists are required to remove cumulus cells early at 4 h after insemination, this may increase the number and duration of gamete operations outside the incubator, consequently, the potential adverse impacts of these procedures on embryonic development remain uncertain [15]. At the same time, the failed-fertilized IVF oocytes had been incubated with sperm for 4–6 h, there is a risk of performing ICSI on fertilized oocytes [16].

Previous literature shows that short-term IVF combined with early R-ICSI could prevent the occurrence of fertilization failure [13, 17, 18]. In order to avoid unexplained fertilization failure, there is a trend to extend short-term IVF combined with early R-ICSI treatment to all patients underwent IVF. However, whether it is necessary to apply short-term IVF to all patients? In this study, we aim to evaluate the effectiveness and safety of short-term insemination, including the effectiveness of short-term IVF combined with early R-ICSI in preventing TFF, as well as the quality of embryos and pregnancy outcomes following transfer of embryos resulting from short-term IVF. Hence, we collaborated with Changzhou Maternal and Child Health Care Hospital to conduct this retrospective analysis, aiming to offer a reference for the clinical implementation of this technology.

Methods

Research subjects

This was a retrospective study from two-centers, the patients undergoing IVF/ ICSI treatment at the Reproductive Obstetrics and Gynecology Center of the Second Affiliated Hospital of Nanjing Medical University and the Reproductive Medicine Center of the Changzhou Maternal and Child Health Care Hospital. A total of 3496 patients were enrolled between January 2016 and December 2022. The data utilized in this study were obtained from the electronic medical records of each individual patient. This study has been approved by the ethics committee of the medical institution, and informed consent was obtained from each participant. All female participants in this study met the following criteria: (1) age < 40 years; (2) underwent their first cycle of IVF/ICSI treatment in our two centers. The exclusion criteria were as follows: (1) frozen oocyte resuscitation cycles; (2) cycles with oocytes in vitro maturation; (3) preimplantation genetic testing cycles; (4) Late-ICSI cycles; (5) cycles using donor oocytes or/and donor sperm. Patients were divided into four groups: (1) Early R-ICSI group: couples accepted short-term IVF combined with early R-ICSI treatment (n = 166); (2) Short-term IVF group: couples only accepted short-term IVF (n = 1656); (3) Routine IVF group: couples accepted routine IVF treatment (n = 1307); (4) ICSI group: couples accepted ICSI treatment (n = 367).

Clinical procedures and oocyte retrieval

An electronic medical record file was generated for infertile patients following pre-pregnancy examinations. After evaluating the age and ovarian reserve of female patients, the attending physician adopts different ovulation induction protocols for them. When the mean diameter of more than two follicles reached 17–18 mm, oocyte maturation was induced by the injection of a 6500IU recombinant human chorionic gonadotropin (r-HCG) for all the patients. Transvaginal and ultrasound-guided follicular aspiration were conducted 36–38 h after HCG injection. Furthermore, the oocytes were incubated in incubators for fertilization. For IVF/ICSI treatment, each patient has provided a signed informed consent form.

Sperm preparation, in-vitro insemination and ICSI

According to World Health Organization standards, semen samples were collected from males after abstinence for 3–5 days on the day of partner oocyte retrieval. Following masturbation, semen was ejaculated into a sterile cup and allowed to liquefy for 30 min at room temperature. In accordance with the WHO guideline, embryologists prepared liquefied semen by routine discontinuous density gradient centrifugation and swim-up procedures. For subsequent fertilization, the processed sperm remained incubated. To allow fertilization to occur naturally, the IVF procedure was typically performed 39–40 h after HCG injection. We incubated each oocyte with about 20,000–30,000/ml motile sperm cells during routine and short-term IVF procedures [13, 19]. Prepared sperm were mixed with oocyte-cumulus complexes for overnight co-incubation for 16–18 h in routine IVF procedure [20, 21]. Conventional ICSI was directly performed 4–6 h after oocyte retrieval. When the patient had previous experienced fertilization failure in other centers before coming to our center for treatment or when his sperm density ≤ 5 × 105/ml after the sperm preparation, the ICSI was directly conducted. The sperms with normal morphology were selected, and then injected into the cytoplasm of metaphase II (MII) oocytes.

Short-term IVF procedure, early second PB assessment, and early R-ICSI

The embryologist observed fertilization under an inverted microscope after co-incubation for 4–6 h. The release of the second polar body was used as an indicator for predicting fertilization. Specifically, after 4 h of insemination, oocytes were denuded from cumulus cells and the oocytes were immediately transferred to fresh cleavage medium for evaluation of fertilization by the presence of a second polar body. In cases where no more than 30% of oocytes released a second polar body, the observation will be extended to 6 h post-fertilization for a re-evaluation. If, at this stage, the percentage remains below 30%, the early R-ICSI will be carried out [22].

Fertilization assessment, embryo evaluation and transfer

On the morning of the first three days after oocyte retrieval, the embryologists checked all the embryos from each cycle. Normal fertilization was defined as the presence of 2PN, while polyspermy referred to oocytes with three pronuclei or more [23]. Day-3 embryos were classified into four levels using the following grading system: Grade 1, embryos with normal embryo developmental speed and blastomeres of equal size and less than 5% fragmentation ; Grade 2, embryos with normal embryo developmental speed and blastomeres of equal or generally equal size and less than 15% fragmentation; Grade 3, embryos with generally normal embryo developmental speed and blastomeres of equal or unequal size and 15–50% fragmentation; and Grade 4, embryos with abnormal embryo developmental speed and blastomeres of unequal size and more than 50% fragmentation. Grade I and II embryos were considered high-quality embryos [19]. Grade I, II and III embryos were considered transferable embryos [24, 25]. Oocyte utilization rate was calculated by the ratio of number of good embryos/number of oocytes retrieved [26]. One or two high-quality embryos were transferred on either day 3 or day 5, and the remaining embryos were used to culture blastocysts, freeze, or ruin. The patient’s preference is taken into consideration for either fresh cleavage or blastocyst transfer. If blastocyst culture was selected, the in-vitro culture would be continued until days 5–6, when the blastocyst formation was observed, the available blastocysts will be frozen or transferred. The grade of blastocyst embryos was evaluated according to Gardner’s criteria [27]. The development stage status of the blastocyst (1-6), the grade of inner cell mass (ICM) (A, B, C), and the grade of trophectoderm (TE) (A, B, C) determined the blastocyst score. Blastocysts with an expansion stage of ≥ 4 and ICM grade higher than C and TE grade higher than C (≥ 4BB) were classified as high-quality. Normally, high-quality blastocyst embryos were preferred selected for transfer [28, 29]. Those patients with endometrial abnormalities, elevated hormone levels, ovarian stimulation syndrome, or purely personal reasons would opt to cancel the transfer and instead choose to freeze the embryos. From the day of oocyte retrieval and continuing for two weeks, progesterone was used for luteal-phase support.

Outcome measures

Pregnancy can be confirmed when elevated serum HCG levels were detected at least twice in a row. After 4 weeks of embryo transfer, clinical pregnancy was considered when ultrasound showed a heartbeat. The implantation rate was defined as the ratio of observed gestational sacs divided by the number of embryos transferred. The clinical pregnancy rate was calculated as the number of clinical pregnancies divided by the number of patients. Miscarriage referred to an intrauterine pregnancy that has not reached 28 weeks of gestation. The neonatal outcome data (gestational weeks, birth weight, sex, etc.) were obtained via telephone interviews with postpartum parents.

Statistical analysis

Statistical analysis was conducted using SPSS 25.0 software (SPSS, USA). When continuous random variables followed a normal distribution, the data were presented as mean ± standard deviation and analyzed through t-test. The categorical variables such as pregnancy outcomes were analyzed by the chi-square test or Fisher exact test. P < 0.05 was considered statistically significant.

Results

In brief, 3496 ovarian stimulation cycles (Routine IVF, n = 1307; Short-term IVF, n = 1656; Early R-ICSI, n = 166; ICSI, n = 367) were analyzed in this study. The study design is shown in Fig. 1. In the process of short co-incubation, there were 166 patients presenting a low fertilization rate of less than 30% and receiving early R-ICSI treatment, accounting for 9.11% of the total.

Fig. 1
figure 1

Flow chart of the study design. IVF: In Vitro Fertilization; ICSI: Intracytoplasmic Sperm Injection; late-ICSI: late Intracytoplasmic Sperm Injection; R-ICSI: Rescue Intracytoplasmic Sperm Injection

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Table 1 displays the baseline characteristics of the routine IVF and short-term IVF groups. There was no significant difference in age or body mass index (BMI) between the two groups of patients. The duration of infertility in the short-term IVF group was found to be significantly longer than that in the routine IVF group. At the same time, the proportion of primary infertility was significantly higher in the short-term IVF group compared to the routine IVF group. The routine IVF group had lower levels of AMH and basal AFC than that in the short-term IVF group, and so as the duration of stimulation and dosage of gonadotrophin.

Table 1 Baseline characteristics of the routine IVF and short-term IVF groups
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Table 2 summarizes the comparisons of laboratory data between the routine IVF and short-term IVF groups. There was a significantly higher number of oocytes retrieved in the short-term IVF group than in the routine IVF group, however, the maturation rate of oocytes was significantly lower than that in the routine IVF group. The embryo cleavage rate in the routine IVF group was significantly lower than that in the short-term IVF group, and the 2PN rate and the 1PN rate in the routine IVF group were significantly higher than that in the short-term IVF group. The rates of ≥ 3PN were similar between the two groups. The transferable embryo rate in the two groups was similar, while the high-quality embryo rate, oocytes utilization rate and blastocyst formation rate were both significantly lower in the short-term IVF group compared with the routine IVF group.

Table 2 Laboratory data of the routine IVF and short-term IVF groups
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Table 3 displays the clinical outcomes and neonatal outcomes of the routine IVF and short-term IVF groups with fresh embryos transferred. There were 402 and 718 fresh embryo transfer cycles in the routine IVF group and short-term IVF group respectively. The clinical outcomes including biochemical pregnancy rate, clinical pregnancy rate, ectopic pregnancy rate, implantation rate, miscarriage rate, ongoing pregnancy rate and live birth rate, did not exhibit significant differences between the two groups. The number of preterm births was found to be similar between the two groups, and there were no significant differences noted in the number of infants categorized by birth weight. Simultaneously, no significant differences were identified in the delivery method of neonates and sex ratio. When dividing the results into single embryo transfer cycles and double embryos transfer cycles for separate calculation, besides sex ratio of single embryo transfer cycles, there were no significant differences in other results between the two groups. The clinical outcomes and neonatal outcomes of the two groups with frozen embryos transferred were shown in Table 4 and were similar to those of fresh embryos. When dividing the results into single embryo transfer cycles and double embryos transfer cycles for separate calculation, besides ongoing pregnancy rate of single embryo transfer cycles, there were no significant differences in other results between the two groups.

Table 3 Clinical outcomes and neonatal outcomes of the routine IVF and short-term IVF groups (fresh embryo)
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Table 4 Clinical outcomes and neonatal outcomes of the routine IVF and short-term IVF groups (frozen embryo)
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In the other two groups, Table 5 displayed the baseline characteristics of the early R-ICSI groups and ICSI groups. The two groups did not exhibit significant differences with respect to patients’ age, BMI, duration of infertility, duration of stimulation, and dosage of gonadotrophin. Moreover, the proportion of primary infertility in the early R-ICSI group was significantly higher than that in the ICSI group. The ICSI group had lower levels of AMH and basal AFC than the early R-ICSI group.

Table 5 Baseline characteristics of the early R-ICSI groups and ICSI groups
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Table 6 summarizes the comparisons of laboratory data between the early R-ICSI and ICSI groups. There was a significantly higher number of oocytes retrieved in early R-ICSI than the ICSI group, which was consistent with the results of AMH and AFC. The maturation rate of oocytes and the embryo cleavage rate were similar in both groups, and the 1 PN rate and the 2PN rate in the ICSI group were significantly higher than that in the early R-ICSI group. The rates of ≥ 3PN were similar between the two groups. There were no significant differences in the rates of transferable embryos, high-quality embryos and oocytes utilization rate between the two groups. However, the blastocyst formation rate in early R-ICSI group was significantly lower than that in the ICSI group.

Table 6 Laboratory data of the early R-ICSI groups and ICSI groups
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The clinical outcomes and neonatal outcomes of the early R-ICSI and ICSI groups with fresh embryos transferred were shown in Table 7, and the frozen embryos were summarized in Table 8. All the clinical outcomes and neonatal outcomes were similar for both fresh and frozen embryos transferred between the two groups. When dividing the results into single embryo transfer cycles and double embryos transfer cycles for separate calculation, there were no significant differences in all results between the two groups.

Table 7 Clinical outcomes and neonatal outcomes of the early R-ICSI groups and ICSI groups (fresh embryo)
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Table 8 Clinical outcomes and neonatal outcomes of the early R-ICSI groups and ICSI groups (frozen embryo)
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Discussion

In 2003, Chen et al. first put forward the concept of early R-ICSI and applied it to clinical practice [30]. The second polar body was released in 80% of fertilized oocytes at 4 h after exposure to spermatozoa and in approximately 90% of fertilized oocytes at 6 h [30, 31]. These results offered a method for early assessment of fertilization occurrence and provided embryologist opportunities.

In couples undergoing IVF, TFF or low fertilization are observed in 5–20% [32]. In this study, the early R-ICSI cycle accounted for 9.11% of all short-term insemination cycles, early R-ICSI benefited these patients. For the past decade, early R-ICSI has been used as one of the solving methods, but its indications are not yet clear. The short-term insemination is adopted for all of the IVF cycles in certain reproductive centers, while some centers use short-term insemination for the first cycle of IVF, and some centers perform short-term insemination when semen parameters are at critical values. In order to avoid unexplained fertilization failure, there is a trend to extend short-term IVF combined with early R-ICSI treatment to all patients underwent IVF. For this reason, we conducted this study.

Primary infertility [7] or longer infertility duration [22] is an important risk factor for TFF. In this study, the proportion of primary infertility and infertility period in the short-term IVF group was notably higher than that in the routine IVF group. At the same time, the proportion of primary infertility in the early R-ICSI group (79.51%) exceeded that in the short-term IVF group (68.05%), while the infertility period in the early R-ICSI group (3.49 years) was higher than that in the short-term IVF group (3.32 years). This may be due to some certain developmental or binding defects in the sperm and oocytes, resulting in TFF or low fertilization in conventional IVF. It is recommended that patients with primary infertility and prolonged infertility, if necessary, should routinely undergo short-term IVF combined with early R-ICSI to reduce the risk of patients with no transferable embryo and avoid the waste of resources. The safety and effectiveness of short-term insemination remain a topic of debate. Compared to overnight insemination, short-term insemination is more difficult to remove granulosa cells around oocytes. Repeated blowing and aspiration of oocytes may have a detrimental effect on the integrity of the oocyte structure, thereby reducing its defense against polyspermy, at the same time, fertilization assessment based on extrusion of the second polar body 6 h after fertilization is not sufficient, because in some cases second polar body degenerates very quickly and cannot be observed, which may lead to a misjudgment of fertilization failure, as previous studies have shown to increased multi-fertilization rate [11, 15]. In this study, the ≥ 3PN rate was similar in the routine IVF group and short-term IVF group, although the ≥ 3PN rate in the early R-ICSI group was higher than that in the ICSI group, the difference was not significant. It may be because the granulosa cells outside the cumulus were not removed prematurely. In this way, the incubation time of sperm and oocytes is relatively long, and the cumulus particles are already relatively loose, which will not cause excessive stimulation and damage to the oocytes during egg disassembly, avoiding the occurrence of multi-fertilization rate. In this study, the 2PN rate of the short-term IVF group was found to be lower than that of the routine IVF group. This difference may be attributed to our center’s frequent selection of short-term insemination for patients with primary infertility, and these patients themselves have the risk of fertilization failure, at the same time, although the fertilization rate is not high, but not meet the criteria of early R-ICSI, these patients have not undergone early R-ICSI, directly impacting the overall fertilization outcome. In addition, the 2PN rate per mature oocyte in the short-term IVF group is 89.47% (15154/16937), the 2PN rate per mature oocyte in the routine IVF group is 87.69% (10632/12125), the 2PN rate per mature oocyte actually higher in the short-term IVF group than that in the routine IVF group(P = 0.000), the possible reason is that there were some immature oocytes affect the overall 2PN rate. Bi-directional communications between an oocyte and cumulus cells play an important role in acquisition of maturation and early embryonic developmental competence following fertilization [15, 33]. In the short-term IVF procedure, cumulus cells were removed early, some oocytes are not fully matured, leading to a reduced rate of mature oocytes. During the routine IVF procedure, the oocytes may reach a better mature state in terms of cytoplasm and nucleus. Therefore, we speculated that the affected oocytes by the timing of cumulus cells removal are the poor-quality oocytes, if synchronization of nuclear and cytoplasmic maturation is achieved at the time of oocyte pick-up, the influence of the cumulus cells becomes less important [34].

In this study, high-quality embryo rate, blastocyst formation rate and oocytes utilization rate in the short-term IVF group were lower than those in the routine IVF group. As mentioned earlier, bi-directional communications between an oocyte and cumulus cells are necessary for the oocyte for the acquisition of maturation and early embryonic developmental competence following fertilization. We speculated that delaying the removal of cumulus cells may improve cytoplasmic maturation or possibly promote the effects of a protective mechanism provided by the cumulus cells thereby enhancing oocyte developmental competence, while short-term insemination removes cumulus cells early, which may affect the maturation of oocytes cytoplasm. This could lead to reduced oocyte maturation rates, consequently affecting high-quality embryo and blastocyst formation rates, reduce the oocytes utilization rate in one single oocyte pick-up cycle. At the same time, we speculated that delaying the removal of cumulus cells could improve embryo development, even in the case of ICSI, several studies have indicated that extending the incubation intervals between oocyte retrieval and oocyte denudation can improve the percentage of mature oocytes, the rates of fertilization and blastocyst formation, which is conducive to embryo development [35,36,37,38]. However, it is crucial to avoid excessive incubation [39], as it has been hypothesized that while fertilization rates may increase beyond the optimal window, but is accompanied by adverse effects on developmental potential [40]. This phenomenon could be linked to in-vitro oocyte aging, characterized by detrimental cellular and molecular alterations [41]. In addition, patients in short-term IVF group were at a higher risk of fertilization failure, which may partially explain why the embryo quality was significantly lower than that of routine IVF group. Therefore, it is not recommended to all IVF cycles [42], for patients with no risk factors for fertilization failure, the outcome of overnight fertilization seems to be more advantageous than that of short-term insemination, and it is still one of the most important ways of insemination worthy of affirmation. In this study, there were no significant differences in clinical outcomes or neonatal outcomes between the two groups, irrespective of whether fresh or frozen embryos were used. This may be due to the fact that in the process of routine IVF, oocytes and sperm usually incubate together overnight, the presence of over physiological quantities of sperm for long-term culture may further increase the ROS level in the culture medium [15, 43], making it impossible to achieve ideal cultivation conditions. High concentrations of ROS may cause DNA fragmentation [44, 45] and both mitochondrial and nuclear DNA injuries [46], adversely affect fertilization rates, embryo quality [47, 48] and the pregnancy rate [49]. Short-term insemination shortens the co-incubation time of oocytes and sperm, which may be more conducive to embryonic development. Consequently, considering the cumulative impact of these factors, both short-term insemination and overnight insemination demonstrated comparable clinical and neonatal outcomes in both fresh and frozen embryo transfer cycles.

In this study, similar high-quality embryos were obtained with early R-ICSI group and the ICSI group, which is consistent with previous research results [30]. Nevertheless, the blastocyst formation rate is lower in the early R-ICSI group. Falcone et al. reported that in terms of fertilization and pregnancy rates, the optimal time for ICSI was 5–6 h after oocyte retrieval [50], some oocytes may have passed the optimal fertilization time when the early R-ICSI performed, thereby affects embryo development. The results in this study showed that early R-ICSI has no negative effect on pregnancy, delivery, and neonatal outcomes both in fresh and frozen embryo transfer cycles. The possible reason is that there is a certain developmental asynchrony in the oocytes retrieved after superovulation. Hence, there are still some oocytes that are in the optimal stage of fertilization during the early R-ICSI period, which may form high-quality embryos after fertilization, thus the pregnancy rate, live birth rate, and neonatal outcome of the early R-ICSI can still achieve similar outcomes to conventional ICSI.

Advantages and limitations

The advantage of this study lies in it conducted in two centers compared with other similar studies, and we conducted a detailed analysis on routine IVF group and short-term IVF group, early R-ICSI group and ICSI group. These findings hold significant value for reproductive physicians and embryologists, providing them with valuable insights and references. However, considering the significant differences in population selection between the two options in our center, short-term insemination was used for individuals with a high likelihood of fertilization failure (primary infertility), while routine overnight insemination was used for secondary infertility with a history of pregnancy. Thus, the potential bias in fundamental factors between the two patient groups could influence the outcomes and interpretations to a certain extent. In the future, well-designed studies with a large sample size are required to further explore the safety and efficacy of short-term insemination.

Conclusion

For patients with primary fertility, short-term IVF combined with early R-ICSI can effectively prevent potential low fertilization or fertilization failure and improve the utilization rate of oocytes in this cycle, reduce the risk of patients with no transferable embryo and avoid resource waste, which is one of the recommendable methods of insemination. However, short-term IVF reduced the oocytes utilization rate in one single oocyte pick-up cycle, for patients with no risk factors for fertilization failure, the overnight insemination is still one of the most important ways of insemination worthy of affirmation. Reproductive physicians and embryologists should adopt personalized insemination methods to avoid fertilization failures and achieve better pregnancy outcomes for patients as much as possible.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Abbreviations

ART:

Assisted Reproductive Technology

IVF-ET:

In Vitro Fertilization Embryo Transfer

IVF:

In Vitro Fertilization

TFF:

Total Fertilization Failure

late R-ICSI:

Late Rescue Intracytoplasmic Sperm Injection

BMI:

Body Mass Index

HCG:

Human Chorionic Gonadotropin

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Acknowledgements

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This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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Author notes

  1. Xinyue Zhang and Yufeng Wang have the same contribution and should be regarded as joint First Authors.

Authors and Affiliations

  1. Reproductive Obstetrics and Gynecology Center of the Second Affiliated Hospital, Nanjing Medical University, 210028, Nanjing, China

    Xinyue Zhang, Jihong Yang, Yangbai Li, Yao Chen, Ting Feng, Suying Li & Yun Qian

  2. Department of Reproductive Medicine Center, Changzhou Maternal and Child Health Care Hospital, Changzhou Medical Center, Nanjing Medical University, Changzhou, 213000, China

    Yufeng Wang, Yingying Yang & Li Chen

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  1. Xinyue Zhang
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Contributions

XYZ and YFW contributed to the data collection and interpretation and the initial draft of the manuscript. JHY contributed to the draft and revision of the manuscript. YBL carried out the semen analysis and processing. YC and YYY contributed to the data collection and analysis. TF and SYL carried out the IVF and ICSI procedure. LC and YQ design of the study and the patient recruitment, and critically revised the manuscript. All authors provided a critical review and approved the final manuscript.

Corresponding authors

Correspondence to Li Chen or Yun Qian.

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Ethics approval and consent to participate

All method was conducted according the ethical standards of the declaration Helsinki. The Reproductive Medicine Ethics Committee of the Second Affiliated Hospital of Nanjing Medical University reviewed and approved this study. Informed consent was obtained from all of the participants.

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Not applicable.

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The authors declare no competing interests.

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Zhang, X., Wang, Y., Yang, J. et al. The clinical value of short-term insemination: a retrospective analysis of 3496 patients. BMC Pregnancy Childbirth 25, 30 (2025). https://doi.org/10.1186/s12884-025-07151-9

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BMC Pregnancy and Childbirth

ISSN: 1471-2393

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