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Lack of Association Between Insulin Resistance and Live Birth Outcomes Among Non- PCOS Women Undergoing Their First Frozen-Thawed Single Blastocyst Transfer: A Retrospective Cohort Study

This retrospective cohort study of 349 non-PCOS women undergoing their first frozen-thawed single blastocyst transfer found no significant association between insulin resistance and live birth outcomes, suggesting that HOMA-IR is not an independent predictor of success in this specific population.

Original authors: Tengfei Wang, Yaojia Zhang, Lijun Peng, Yun Le, Sheng Yang, Mengyi Zhu

Published 2026-09-28

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CC BY 4.0

Original authors: Tengfei Wang, Yaojia Zhang, Lijun Peng, Yun Le, Sheng Yang, Mengyi Zhu

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

In the complex world of helping people conceive, doctors often look for hidden metabolic hurdles that might be blocking the way. One such hurdle is insulin resistance, a condition where the body struggles to use insulin effectively to manage blood sugar. When this happens, the body produces extra insulin to compensate, which can disrupt the delicate hormonal balance needed for reproduction. This issue is well-known in women with polycystic ovary syndrome, a common cause of infertility, where high levels of insulin are linked to lower chances of a successful pregnancy. Because of this strong link in that specific group, many clinics have begun checking for insulin resistance in all patients before transferring an embryo, hoping that fixing this metabolic issue will improve the odds of a baby being born.

However, a new study from a reproductive center in China suggests that this approach might not be necessary for everyone. The researchers focused on a group of women who did not have polycystic ovary syndrome and were undergoing their very first attempt at a frozen embryo transfer. In this procedure, an embryo created in a lab is thawed and placed into the uterus. The team wanted to see if the women with insulin resistance had different outcomes than those without it. They looked at 349 women, dividing them into two groups based on a standard blood test that measures how well their bodies handle sugar. One group had higher levels of insulin resistance, while the other had lower levels. The researchers then tracked how many women in each group successfully gave birth to a live baby.

The results were strikingly clear. The rate of live births was almost exactly the same in both groups. About 38 percent of the women with insulin resistance had a baby, and 37.7 percent of the women without it had a baby. The difference was so small that it was statistically indistinguishable from random chance. When the researchers adjusted their analysis to account for other factors that could influence the outcome, such as the age of the woman, her body mass index, the quality of the embryo, and the thickness of the uterine lining, insulin resistance still did not appear to be a predictor of success or failure. The study also examined whether the risk changed as insulin resistance became more severe, but the data showed a flat line; there was no dose-response relationship where higher resistance led to worse outcomes.

This finding challenges the idea that insulin resistance is a universal barrier to pregnancy for all women. The authors suggest that the impact of this metabolic condition may depend heavily on the specific population being studied. In women who have already failed multiple embryo transfers or who are obese, insulin resistance might act as a significant stressor that lowers the chances of success. But for women who are healthy, have not had prior failures, and are undergoing their first transfer, their bodies may have enough natural resilience to overcome mild to moderate insulin resistance. The study indicates that for this specific group, the metabolic issue does not seem to interfere with the final goal of having a live birth.

Consequently, the researchers propose that routine screening for insulin resistance before a first embryo transfer might not be useful for women without other risk factors. They argue that medical resources should be focused on high-risk groups, such as those with a history of repeated implantation failure or obesity, where correcting insulin resistance has been shown to make a real difference. For the first-time patient without these additional challenges, the study suggests that the body's natural capacity to carry a pregnancy is likely sufficient, regardless of whether insulin resistance is present. This does not mean insulin resistance is harmless, but rather that its effect on reproductive success is not a one-size-fits-all problem. The study concludes that doctors should consider the patient's history and overall risk profile before deciding whether to test for and treat this metabolic condition.

Technical Summary: Lack of Association Between Insulin Resistance and Live Birth Outcomes Among Non-PCOS Women Undergoing Their First Frozen-Thawed Single Blastocyst Transfer

Problem Statement
Insulin resistance (IR) is a well-established metabolic disturbance in women with Polycystic Ovary Syndrome (PCOS), where it is linked to reduced live birth rates and increased miscarriage risks following assisted reproductive technology (ART). The biological mechanisms are understood to involve hyperinsulinemia-induced androgen excess, impaired oocyte maturation, and compromised endometrial receptivity. However, the clinical significance of IR in non-PCOS populations remains inconclusive. While some studies suggest IR does not affect ART outcomes in general non-PCOS cohorts, others indicate it may impair outcomes in high-risk subgroups (e.g., recurrent implantation failure or obesity). Crucially, there is a lack of systematic evaluation regarding IR in first-cycle non-PCOS patients who have no history of failed implantation. It is unclear whether IR impacts live birth outcomes in this specific population, which may possess preserved reproductive and metabolic reserves.

Methodology
This study employed a single-center, retrospective cohort design involving 349 non-PCOS infertile women of Chinese Han ethnicity undergoing their first frozen-thawed single blastocyst transfer (FET) between June 2020 and June 2025 at Huzhou Maternity & Child Health Care Hospital.

Grouping: Patients were stratified into an Insulin Resistance (IR) group ( $n=142$ ) and a non-IR group ( $n=207$ ) based on the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). The cutoff of HOMA-IR ≥ 2.71 was utilized, derived from a previous large-scale study validating this threshold as the upper quartile for non-PCOS Chinese women and associating it with late miscarriage risk.
Outcomes: The primary outcome was live birth rate. Secondary outcomes included clinical pregnancy rate and early miscarriage rate.
Statistical Analysis:
- Multivariate Logistic Regression: Hierarchical models were constructed to adjust for confounders (age, BMI, blastocyst quality, endometrial thickness).
- Dose-Response Analysis: Restricted cubic spline (RCS) analysis evaluated the relationship between HOMA-IR as a continuous variable and live birth.
- Predictive Value: Receiver Operating Characteristic (ROC) curve analysis assessed the predictive capability of HOMA-IR for live birth.
- Robustness Checks: Subgroup/interaction analyses (IR × BMI, IR × age), sensitivity analyses (excluding BMI > 28 kg/m² and using an alternative cutoff of ≥2.5), and post-hoc power analysis were conducted.

Key Results
The study found no statistically significant association between insulin resistance and live birth outcomes in this specific population:

Live Birth Rates: The live birth rate was nearly identical between groups: 38.0% (54/142) in the IR group versus 37.7% (78/207) in the non-IR group ( $P = 1.000$ ).
Multivariate Analysis: After adjusting for age, BMI, blastocyst quality, and endometrial thickness, IR was not an independent predictor of live birth (Adjusted OR = 1.16, 95% CI: 0.71–1.92, $P = 0.549$ ).
Dose-Response: Restricted cubic spline analysis revealed a flat curve across the HOMA-IR distribution, indicating no significant dose-response relationship between HOMA-IR levels and live birth probability.
Predictive Value: ROC analysis showed poor predictive ability of HOMA-IR for live birth (AUC = 0.533, 95% CI: 0.469–0.598), effectively no better than chance.
Secondary Outcomes: While the IR group showed a non-significant trend toward higher clinical pregnancy (55.6% vs. 46.9%) and higher early pregnancy loss (16.2% vs. 9.2%), these differences did not reach statistical significance after Bonferroni correction.
Robustness: Sensitivity analyses excluding obese patients (BMI > 28) and using alternative HOMA-IR cutoffs yielded consistent null results. Interaction analyses confirmed that the lack of association was not modified by age or BMI.

Key Contributions

Population-Specific Evidence: This is the first study to specifically focus on non-PCOS patients undergoing their first FET cycle, providing the largest dataset (n=349) to date for this specific demographic.
Comprehensive Statistical Approach: The study moves beyond simple binary comparisons by employing hierarchical regression, restricted cubic spline analysis for dose-response evaluation, and ROC analysis for predictive utility, forming a robust chain of evidence.
Validation of Null Findings: By transparently reporting null findings with rigorous statistical adjustment and sensitivity checks, the study counters publication bias in reproductive medicine.
Refined Cutoff Application: The study applies a previously validated, population-specific HOMA-IR cutoff (≥2.71) to a new clinical context, enhancing the applicability of findings to Chinese non-PCOS populations.

Significance and Clinical Implications
The authors conclude that in non-PCOS patients undergoing their first FET cycle, insulin resistance is not associated with live birth outcomes. They propose that the impact of IR on reproductive outcomes is population-specific and may follow a "threshold-amplification" model:

Low-Risk Populations: In first-cycle patients without prior failure, preserved endometrial receptivity and metabolic reserves may compensate for mild-to-moderate IR, rendering its negative effects undetectable in terms of final live birth.
High-Risk Populations: Conversely, IR remains clinically significant in high-risk groups (e.g., recurrent implantation failure, obesity), where it synergizes with existing vulnerabilities to impair outcomes.

Clinical Recommendation: Based on these findings, the authors suggest that routine HOMA-IR screening prior to the first FET cycle in non-PCOS patients without additional risk factors (such as RIF or obesity) may have limited clinical utility. Instead, they advocate for a risk-stratified approach, reserving metabolic screening and potential metformin interventions for high-risk subgroups where the evidence for benefit is established. This strategy aims to optimize resource allocation and avoid unnecessary patient anxiety in low-risk populations.

Technical Summary: Lack of Association Between Insulin Resistance and Live Birth Outcomes Among Non-PCOS Women Undergoing Their First Frozen-Thawed Single Blastocyst Transfer

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