Association of number of retrieved oocytes with live birth rate and birth weight: an analysis of 231,815 cycles of in vitro fertilization

Evaluating the Utility of Intralipid Infusion to Improve Live Birth Rates in Patients with Recurrent Pregnancy Loss or Recurrent Implantation Failure

Context

Intralipid is used to improve clinical outcomes in patients with recurrent pregnancy loss (RPL) or recurrent implantation failure (RIF) with elevated natural killer (NK) cells. Data supporting this practice is conflicting but suggestive of minimal benefit.

Aims

The aims of this study are to determine if intralipid infusion improves live birth rates and if is a cost-effective therapy in the RPL/RIF population.

Settings and Design

This was a large REI private practice, retrospective cohort study.

Subjects and Methods

Charts of 127 patients who received intralipid from 2012 to 2015 were reviewed and compared to historical control data. T-tests and Chi-square analyses evaluated demographics and cycle statistics. Chi-square analyses assessed impact on clinical pregnancy and live birth rates. Cost analysis was performed from societal perspective with a one-way sensitivity analysis.

Results

Patients with live births were noted to have a higher average number of previous live births and were more likely to have had a frozen embryo transfer in the intralipid cycle in comparison to those with unsuccessful pregnancy outcomes. Neither clinical pregnancy nor live birth rates were significantly improved from baseline rates quoted in the literature (P = 0.12 and 0.80, respectively). Intralipid increased costs by $681 per live birth. If live birth rates were >40% using intralipid and <51% without intervention, neither strategy was favored.

Conclusions

Intralipid does not improve live birth rates and is not cost-effective for patients with RIF or RPL and elevated NK cells. This study supports the growing literature demonstrating the minimal benefit of screening for and treating elevated peripheral NK cells.

Development of in vitro maturation techniques for clinical applications

In vitro maturation (IVM) refers to maturation in culture of immature oocytes at different stages that may or may not have been exposed to short courses of gonadotropins. The source of immature oocytes is an important feature for subsequent embryonic development, pregnancy, and healthy live births. IVM is an effective treatment that has already achieved significant outcomes of acceptable pregnancy and implantation rates and has led to the births of several thousand healthy babies. As the development of IVM treatment continues, an attractive possibility for improving the already successful outcome is to combine a natural-cycle in vitro fertilization (IVF) treatment with immature-oocyte retrieval followed by IVM of those immature oocytes. If the treatment processes can be simplified for immature-oocyte retrieval, different types of infertile women may be able to take advantage of these treatments. Mild-stimulation IVF combined with IVM treatment may represent a viable alternative to the standard treatment. Although IVM treatment is still considered to be experimental, it is now time to reconsider the IVM technology and its development. Mild-stimulation IVF combined with IVM may prove to be not just alternatives to standard treatments, but potentially first-line treatment choices.

Frozen embryo transfer can be performed in the cycle immediately following the freeze-all cycle

PURPOSE

In this study, we investigated whether the time interval between oocyte retrieval and frozen embryo transfer (FET) affected the live birth (LB) rates of human segmented-IVF cycles.

METHOD

A total of 1338 ICSI freeze-all cycles were performed between February 2015 and January 2016, with 1121 FET cycles being retrospectively analyzed. All vitrified-warmed blastocyst transfers were performed in artificial FET cycles, using gonadotropin-releasing hormone (GnRH) agonist downregulation and oral estrogen endometrial preparation. The primary outcome measure was LB. Cycles were investigated in oocyte retrieval-to-FET interval groups of 32-46, 47-61, 62-76, 77-91, and ≥ 92 days, with the 47-61-day group used as the reference group.

RESULTS

There were no significant differences in LB rates between the groups in the overall analysis, as well as, in sub-analyses investigating LB in terms of single blastocyst transfer (SBT), trigger type (GnRH agonist, triggers including hCG), oocyte number (≤ 5 and ≥ 15), and maternal age (> 35 years).

CONCLUSION

The present study showed that it is feasible to perform transfers 36 days after oocyte retrieval and that delaying FET in freeze-all beyond the cycle immediately following oocyte retrieval does not increase LB rates.

Pregnancy, birth, and infant outcomes by maternal fertility status: the Massachusetts Outcomes Study of Assisted Reproductive Technology

BACKGROUND

Births to subfertile women, with and without infertility treatment, have been reported to have lower birthweights and shorter gestations, even when limited to singletons. It is unknown whether these decrements are due to parental characteristics or aspects of infertility treatment.

OBJECTIVE

The objective of the study was to evaluate the effect of maternal fertility status on the risk of pregnancy, birth, and infant complications.

STUDY DESIGN

All singleton live births of ≥22 weeks' gestation and ≥350 g birthweight to Massachusetts resident women in 2004-2010 were linked to hospital discharge and vital records. Women were categorized by their fertility status as in vitro fertilization, subfertile, or fertile. Women whose births linked to in vitro fertilization cycles from the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System were classified as in vitro fertilization. Women with indicators of subfertility but not treated with in vitro fertilization were classified as subfertile. Women without indicators of subfertility or in vitro fertilization treatment were classified as fertile. Risks of 15 adverse outcomes (gestational diabetes, pregnancy hypertension, antenatal bleeding, placental complications [placenta abruptio and placenta previa], prenatal hospitalizations, primary cesarean delivery, very low birthweight [<1500 g], low birthweight [<2500 g], small-for-gestation birthweight [z-score ≤-1.28], large-for-gestation birthweight [z-score ≥1.28], very preterm [<32 weeks], preterm [<37 weeks], birth defects, neonatal death [0-27 days], and infant death [0-364 days of life]) were modeled by fertility status with the fertile group as reference and the subfertile group as reference, using multivariate log binomial regression and reported as adjusted risk ratios and 95% confidence intervals.

RESULTS

The study population included 459,623 women (441,420 fertile, 8054 subfertile, and 10,149 in vitro fertilization). Women in the subfertile and in vitro fertilization groups were older than their fertile counterparts. Risks for 6 of 6 pregnancy outcomes and 6 of 9 infant outcomes were increased for the subfertile group, and 5 of 6 pregnancy outcomes and 7 of 9 infant outcomes were increased for the in vitro fertilization group. For 4 of the 6 pregnancy outcomes (uterine bleeding, placental complications, prenatal hospitalizations, and primary cesarean) and 2 of the infant outcomes (low birthweight and preterm) the risk was greater in the in vitro fertilization group, with nonoverlapping confidence intervals to the subfertile group, indicating a substantially higher risk among in vitro fertilization-treated women. The highest risks for the in vitro fertilization women were uterine bleeding (adjusted risk ratio, 3.80; 95% confidence interval, 3.31-4.36) and placental complications (adjusted risk ratio, 2.81; 95% confidence interval, 2.57-3.08), and for in vitro fertilization infants, very preterm birth (adjusted risk ratio, 2.13; 95% confidence interval, 1.80-2.52), and very low birthweight (adjusted risk ratio, 2.15; 95% confidence interval, 1.80-2.56). With subfertile women as reference, risks for the in vitro fertilization group were significantly increased for uterine bleeding, placental complications, prenatal hospitalizations, primary cesarean delivery, low and very low birthweight, and preterm and very preterm birth.

CONCLUSION

These analyses indicate that, compared with fertile women, subfertile and in vitro fertilization-treated women tend to be older, have more preexisting chronic conditions, and are at higher risk for adverse pregnancy outcomes, particularly uterine bleeding and placental complications. The greater risk in in vitro fertilization-treated women may reflect more severe infertility, more extensive underlying pathology, or other unfavorable factors not measured in this study.

Total number of oocytes and zygotes are predictive of live birth pregnancy in fresh donor oocyte in vitro fertilization cycles

OBJECTIVE

To evaluate the association of oocyte donor-recipient characteristics, oocyte donor response, and live birth pregnancy rate following fresh donor oocyte IVF-ET.

DESIGN

Retrospective cohort study.

SETTING

Academic reproductive medicine practice.

PATIENT(S)

Two hundred thirty-seven consecutive fresh donor oocyte IVF-ET cycles from January 1, 2007 to December 31, 2013 at the Massachusetts General Hospital Fertility Center.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live birth rate per cycle initiated.

RESULT(S)

The mean (±SD) age of oocyte donors and recipients was 27.0 ± 3.7 and 41.4 ± 4.6 years, respectively. Oocyte donor demographic/reproductive characteristics, ovarian reserve testing, and peak serum E₂ during ovarian stimulation were similar among cycles which did and did not result in live birth, respectively. Overall implantation, clinical pregnancy, and live birth pregnancy rates per cycle initiated were 40.5%, 60.8%, and 54.9%, respectively. The greatest probability of live birth was observed in cycles with >10 oocytes retrieved, mature oocytes, oocytes with normal fertilization (zygote-two pronuclear stage), and cleaved embryos.

CONCLUSION(S)

The number of oocytes (total and mature), zygotes, and cleaved embryos are associated with live birth following donor oocyte IVF cycles. These findings suggest that specific peri-fertilization factors may be predictive of pregnancy outcomes following donor oocyte IVF cycles.

Endometrial injury, the quality of embryos, and blastocyst transfer are the most important prognostic factors for in vitro fertilization success after previous repeated unsuccessful attempts

Purpose

The purpose of this study was to find out the most important prognostic factors for achieving a pregnancy after in vitro fertilization (IVF) in women with history of repeated unsuccessful IVF attempts.

Methods

We analyzed factors affecting pregnancy rate in a retrospective study including 429 IVF/ICSI cycles performed in women younger than 40 years with at least three previous consecutive failed IVF/ICSI attempts.

Results

Clinical pregnancy was observed in 140/429 (32.6%) cycles. Clinical pregnancy rate (CPR) was significantly higher in cycles with LEI compared to cycles without LEI before embryo transfer (44.4 vs 26.54%, p = 0.007). The CPR was also higher in cycles with day 5 blastocyst- compared with day 3 cleavage-stage embryo transfers (45.51 vs 26.54%, p < 0.001). In multivariate logistic regression model, only transfer of at least one good quality embryo (OR = 4.32, 95% CI 2.41–7.73), local endometrial injury (OR = 1.73, 95% CI 1.02–2.92), and transfer on day 5 (OR = 3.02, 95% CI 1.53–5.94) remained important independent prognostic factors for clinical pregnancy.

Conclusions

These results suggest that hysteroscopy with local injury to the endometrium prior to ovarian stimulation for IVF/ICSI can improve implantation and pregnancy rates in women experiencing recurrent IVF failure. However, large studies are needed to confirm these findings.

Perinatal outcomes after oocyte donation and in-vitro fertilization

PURPOSE OF REVIEW

To critically appraise the existing literature on perinatal outcomes following oocyte donation (OD) pregnancies and compare it with autologous in-vitro fertilization (IVF) pregnancies.

RECENT FINDINGS

OD pregnancies are at higher risk of developing hypertensive disorders compared with autologous IVF. The risk of preterm birth and low birth weight is higher with singleton and multiple OD compared with autologous IVF pregnancies. There is no increased risk of congenital malformations following OD compared with autologous IVF births.

SUMMARY

OD pregnancies are at higher risk of developing hypertensive disorders and adverse perinatal outcomes compared with autologous IVF.

Ovarian stimulation protocols for IVF: is more better than less?

Conventional ovarian stimulation protocols for IVF are designed to achieve maximum oocyte yields. Conventional protocols, however, are associated with patient discomfort, increased risk of ovarian hyperstimulation syndrome and higher costs. In recent years, mild stimulation protocols have risen in popularity. These protocols typically use lower doses (≤150 IU/day), shorter duration of exogenous gonadotrophins, or both, compared with conventional protocols, with the goal of limiting the number of retrieved oocytes to less than eight. The pregnancy rate per cycle (fresh embryo transfer only) is lower with mild stimulation compared with conventional stimulation; however, the cumulative pregnancy rate seems to be comparable between the approaches. Reports are conflicting on the effects of mild versus conventional stimulation on embryo quality. This article expands on a live debate held at the American Society for Reproductive Medicine 2015 Annual Meeting to compare the advantages and disadvantages of the 'more is better' (conventional protocol) versus 'less is best' (mild protocol) approaches to ovarian stimulation. Both protocols are associated with benefits and challenges, and physicians must consider the needs of the individual patient when determining the best treatment options. Further prospective studies comparing a variety of outcomes with conventional and mild stimulation are needed.

Factors predicting double embryo implantation following double embryo transfer in assisted reproductive technology: implications for elective single embryo transfer

PURPOSE

The aim of this study was to identify factors associated with double embryo implantation following double embryo transfer (DET) during assisted reproductive technology (ART) procedures and to evaluate the implications of findings in selecting candidates for elective single embryo transfer (eSET).

METHODS

Factors predicting double embryo implantation, defined as embryo transfers with two or more heartbeats on 6-week ultrasound following DET, were assessed using the US National ART Surveillance System data from 2000 to 2012 (n = 1,793,067 fresh, autologous transfers). Adjusted risk ratios (aRRs) were estimated after stratifying by prognosis. Favorable prognosis was defined as first-time ART with supernumerary embryo(s) cryopreserved. Average prognosis was defined as first-time ART without supernumerary embryo(s) cryopreserved, prior unsuccessful ART with supernumerary embryo(s) cryopreserved, or prior ART with previous birth(s) conceived with ART or naturally. Rates and factors associated with double embryo implantation were compared with single embryo implantation following DET among both prognosis groups.

RESULTS

Double embryo implantation was positively associated with blastocyst (versus cleavage) transfer in favorable (aRR = 1.58 (1.51-1.65)) and average (aRR = 1.67 (1.60-1.75)) prognosis groups and negatively associated with age >35 years in both prognosis groups. For average prognosis patients, double embryo implantation was associated with retrieving >10 oocytes (aRR = 1.22 (1.18-1.24)).

CONCLUSIONS

Regardless of prognosis, patients aged <35 years with blastocyst-stage embryos and average prognosis patients from whom >10 oocytes were retrieved may be good candidates for eSET. Physicians may consider using these data to counsel patients on eSET, which would reduce multiple gestations and associated complications.

Collection of pregnancy outcome records following infertility-challenges and possible solutions

PURPOSE

The aim of this study is to report challenges encountered when conducting inter-institutional data collection of obstetric (prenatal and postpartum) and delivery outcomes for research purposes and to propose solutions for enhanced efficiency.

METHODS

Data were collected from women who consented to collection of obstetric and delivery records for an observational study of pregnancy and delivery outcomes following infertility treatment. We analyzed key issues relevant to improving efficiency of obstetric and delivery data collection via quantification of effort (such as number of calls and faxes) required to obtain records from different types of obstetric clinics and hospitals before and after utilization of a revised authorization.

RESULTS

At time of analysis, records were successfully collected from 320 of the 451 participants who had delivered. The 320 participants received obstetric care at 63 institutions and delivered at 27 hospitals, with 168 (52.5 %) delivering at institutions other than home facility. At time of consent (8 weeks gestation), 155 of 320 (48.5 %) correctly predicted where they would receive obstetric care and 176 (55 %) where they would delivery. Most facilities (nearly 90 %) rejected our original authorization, but most (90 %) accepted the revised authorization described in this manuscript.

CONCLUSIONS

Collecting records is time-consuming but important as over 50 % of our participants received care outside of the home facility. To efficiently collect outside records, we recommend that researchers interested in maternal and neonatal outcomes consider the guidelines outlined in this manuscript. This report also provides strong evidence of the need to develop data sharing through electronic health records for research purposes.

Natural cycle IVF reduces the risk of low birthweight infants compared with conventional stimulated IVF

STUDY QUESTION

Are perinatal outcomes improved in singleton pregnancies resulting from fresh embryo transfers performed following unstimulated/natural cycle IVF (NCIVF) compared with stimulated IVF?

SUMMARY ANSWER

Infants conceived by unstimulated/NCIVF have a lower risk of being low birthweight than infants conceived by stimulated IVF; however, this risk did not remain significant after adjusting for gestation age.

WHAT IS ALREADY KNOWN

Previous studies have shown that infants born after modified NCIVF have a higher average birthweight and are less likely to be low birthweight than those infants conceived with conventional stimulated IVF.

STUDY DESIGN, SIZE AND DURATION

Retrospective cohort study of singleton live births in non-smoking women undergoing fresh IVF-embryo transfer cycles from 2007 to 2013 in a single IVF center. The women were stratified by stimulated (n = 174) or unstimulated (n = 190) IVF exposure status. Unstimulated/NCIVF is defined as IVF without the use of exogenous gonadotrophins, and only includes the use of HCG to time oocyte retrieval.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Demographic data including maternal age, BMI, infertility diagnosis and IVF cycle characteristics were collected. The perinatal outcomes used for comparison between the two study groups were length of gestation, birthweight, preterm delivery, very preterm delivery, low birthweight, small for gestational age and large for gestational age.

MAIN RESULTS AND ROLE OF CHANCE

Although women in the NCIVF group were older than those in the stimulated group (35.0 versus 34.2 years, P < 0.05), parity and history of prior ART cycles were comparable between the groups. The mean birthweight was significantly higher in the NCIVF group by 163 g than in the stimulated group (3436 ± 420 g versus 3273 ± 574 g, P < 0.05). Consistent with this finding, there were also less low birthweight (<2500 g) infants in the NCIVF group versus stimulated group (1 versus 8.6%, P < 0.005). The reduction in risk for low birthweight in the NCIVF group remained significant after adjustment for maternal age, infertility diagnosis, ICSI, number of embryos transferred and blastocyst transfer (odds ratio (OR) 0.07; 95% CI 0.014-0.35). As NCIVF group had less preterm infants, additional adjustment for gestational age was performed and this showed a tendency towards lower risk of low birthweight in NCIVF (OR 0.11; 95% CI 0.01-1.0). While gestational age at delivery was comparable between the groups, both preterm births (<37 weeks gestation) (31 versus 42%, P < 0.05) and very preterm births (<32 weeks gestation) (0.52 versus 6.3%, P < 0.005) were significantly reduced in the NCIVF group. However, after adjustment for potential confounders, the reduction in risk of preterm and very preterm delivery associated with the NCIVF group was no longer significant (OR 1.1; 95% CI 0.48-2.5).

LIMITATIONS, REASONS FOR CAUTION

Limitations of this study are the retrospective nature of the data collection and the lack of information about parental characteristics associated with birthweight.

WIDER IMPLICATIONS OF THE FINDINGS

The improved perinatal outcomes following successful unstimulated/NCIVF suggest that this treatment should be considered as a viable option for infertile couples. NCIVF could reduce potential adverse perinatal outcomes such as low birthweight related to fresh embryo transfers performed following ovarian stimulation. The etiology of the improved perinatal outcomes following NCIVF needs to be explored further to determine if the improvement is derived from endometrial factors versus follicular/oocyte factors.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by the following grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, NICHD K12HD047018 (W.M.), NICHD K12HD001271 (L.A.K.). The authors have no competing interests.

Conventional ovarian stimulation and single embryo transfer for IVF/ICSI. How many oocytes do we need to maximize cumulative live birth rates after utilization of all fresh and frozen embryos?

STUDY QUESTION

What is the impact of ovarian response on cumulative live birth rates (LBR) following utilization of all fresh and frozen embryos in women undergoing their first ovarian stimulation cycle, planned to undergo single embryo transfer (SET).

SUMMARY ANSWER

Cumulative LBR significantly increases with the number of oocytes retrieved.

WHAT IS KNOWN ALREADY

Several studies have addressed the issue of the optimal number of oocytes retrieved following controlled ovarian stimulation (COS) for IVF/ICSI and demonstrated that ovarian response is independently related to LBR following IVF/ICSI. The vast majority of studies pertained only to the outcome of the fresh IVF cycle and did not evaluate the cumulative LBR following the transfer of all fresh and frozen-thawed embryos after a single ovarian stimulation, which is the most meaningful outcome for the infertile patient.

STUDY DESIGN, SIZE, DURATION

This study is a large cohort analysis of retrospective data from January 2009 to December 2013 in a tertiary medical centre, at the Centre for Reproductive Medicine at the University Hospital of Brussels.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study included 1099 eligible consecutive women 18-40 years old undergoing their first IVF cycle and planned to undergo SET in their fresh cycle. All patients were treated with a conventional starting gonadotrophin dose of 150-225 IU recombinant FSH (rFSH) in a fixed GnRH antagonist protocol. Vitrification was used as cryopreservation method. To evaluate the impact of oocyte yield on fresh LBR and on cumulative LBR after utilization of all cryopreserved embryos, patients were categorized into four groups according to the number of oocytes retrieved: 1-3 (Group A), 4-9 (Group B), 10-15 (Group C) or >15 oocytes (Group D).

MAIN RESULTS AND THE ROLE OF CHANCE

Regarding LBR in the fresh IVF/ICSI cycles, unadjusted results did not show any significant difference when comparing either high (>15 oocytes) versus normal (10-15 oocytes) (P = 0.65), or normal (10-15) versus suboptimal (4-9 oocytes) responders (P = 0.2). LBR in the fresh cycles were significantly higher (P < 0.05) in high, normal and suboptimal responders when compared with the low ovarian responder group (1-3 oocytes). Moderate-severe ovarian hyperstimulation syndrome occurred in 11 out of 1099 patients (1%). The cumulative LBR significantly increased with the number of oocytes retrieved (χ(2) test for trend P < 0.001). High responders (>15 oocytes) demonstrated a significantly higher LBR not only versus poor (0-3 oocytes) (P < 0.001) and suboptimal (4-9) responders (P < 0.001), but also versus women with normal (10-15) ovarian response (P = 0.014). Finally, although suboptimal responders had a better outcome compared with poor ovarian responders (P = 0.002), this group had a significantly lower cumulative LBR compared with normal ovarian responders (P = 0.02). Multivariate logistic regression analysis showed that the ovarian response category remained an independent predictive factor (P < 0.001) for cumulative LBR.

LIMITATIONS, REASONS FOR CAUTION

This is a cohort analysis based on retrospective data collection. Despite our robust methodological approach, the presence of biases related to retrospective design cannot be excluded. High responders may inherently have had a better prognosis. In addition, we cannot provide any guidance for patients undergoing either multiple embryo transfers or treated with higher gonadotrophin doses.

WIDER IMPLICATIONS OF THE FINDINGS

Women undergoing COS for their first IVF/ICSI cycle and SET should be informed that, although the number of oocytes retrieved does not affect LBR in the fresh cycle, the higher the oocyte yield, the higher the probability to achieve a live birth after utilization of all cryopreserved embryos. Large cohort studies are needed in order to confirm our results of cumulative LBR in different ovarian stimulation settings with higher stimulation doses.

STUDY FUNDING/COMPETING INTERESTS

No external funding was used for this study. No conflicts of interest are declared.

Optimum oocyte retrieved and transfer strategy in young women with normal ovarian reserve undergoing a long treatment protocol: a retrospective cohort study

PURPOSE

This study aimed to investigate the relationship between the number of oocytes retrieved and clinical outcomes in young women with normal ovarian reserve who were undergoing their first in vitro fertilization and embryo transfer (IVF-ET) cycle. The transfer strategy based on yielded oocytes was also discussed in this article.

METHODS

A total of 1567 patients who underwent first long protocol of IVF treatment in our reproductive medical center between January 2010 and June 2014 were categorized into five groups based on the retrieved oocyte number, namely, 4∼6, 7∼9, 10∼12, 13∼15, and ≥16. Baseline parameters were similar among the groups. Primary outcome was defined as the cumulative live birth rate (CLBR), and secondary outcomes included the rate of patients with high risks for ovarian hyperstimulation syndrome (OHSS).

RESULTS

It was found that the CLBR increased with the number of oocytes, as well as the rate for high risks of OHSS. In fresh cycles, 10∼12 oocyte group demonstrated the highest implantation rate (53.32 %), clinical pregnancy rate (CPR) (73.13 %), and live birth rate (LBR) (61.14 %), with no significant differences. Moreover, both cumulative CPR (CCPR) and CLBR became significantly higher in the 10∼12 oocyte group, compared with 4∼6 and 7∼9 groups. However, when the retrieved oocytes increased to 13∼15 or ≥16, the cumulative results did not have a significant increase. Also, the high risk rate of OHSS was much lower in the 10∼12 group (11.53 %) than that in the 13∼15 group (29.97 %) and ≥16 group (77.30 %). Unconditional multivariate logistic regression analysis showed that when ≥10 oocytes were retrieved, the CLBR increased significantly (P < 0.01). When oocyte number exceeded 16, the CPR of frozen embryo transfer cycle was much higher than that of fresh cycle (P < 0.05).

CONCLUSIONS

For young women with normal ovarian reserve, retrieving 10∼12 oocytes might result in optimized pregnancy outcomes in a fresh cycle with low OHSS risk and would not compromise cumulative outcomes. When ≥16 oocytes were retrieved, a "freeze-all" embryo strategy might be preferable.