Highlights
- Women with Polycystic Ovary Syndrome (PCOS) exhibit significantly higher concentrations of Monocyte Chemoattractant Protein-1 (MCP1) and Fatty Acid Binding Protein-4 (FABP4) in early pregnancy.
- The elevation of these biomarkers is primarily mediated by maternal Body Mass Index (BMI), suggesting that adiposity is a more significant driver of inflammation than the PCOS diagnosis itself during gestation.
- Despite the metabolic shifts, neither MCP1 nor FABP4 levels were found to interact with or predict adverse maternal or neonatal outcomes in this cohort.
- The findings underscore the necessity of pre-conception weight optimization for women with PCOS to mitigate systemic inflammatory and metabolic stress.
Background: The Metabolic Complexity of PCOS in Gestation
Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder among women of reproductive age, characterized by androgen excess, ovulatory dysfunction, and polycystic ovarian morphology. Beyond its impact on fertility, PCOS is increasingly recognized as a systemic metabolic condition associated with insulin resistance, dyslipidemia, and chronic low-grade inflammation. When women with PCOS conceive, they face a heightened risk of pregnancy-related complications, including gestational diabetes mellitus (GDM), preeclampsia, and preterm birth.
The transition into pregnancy involves profound physiological shifts in metabolic and inflammatory regulation. In a healthy pregnancy, these changes support fetal growth and prepare the maternal body for the demands of labor. However, in women with pre-existing metabolic dysfunction, such as those with PCOS, these pathways may become exaggerated or maladaptive. Identifying specific biomarkers in early pregnancy that signal these risks is a priority for clinicians seeking to personalize prenatal care and improve outcomes. Until recently, the degree to which PCOS independently alters the inflammatory milieu of early pregnancy—separate from the influence of obesity—remained a subject of intense debate.
Study Design and Methodology
To address these questions, researchers conducted a cross-sectional study using pooled baseline data from two prominent international multicentre clinical trials: the IMPACT DIABETES B2B&ME and the TOBOGM (Treatment of Booking Gestational Diabetes Mellitus) study. The analysis included 151 pregnant women at less than 24 weeks’ gestation who were identified as being at risk for GDM. Within this cohort, 65 women had a confirmed diagnosis of PCOS, while 86 served as the control group without PCOS.
The study aimed to profile a comprehensive panel of biomarkers associated with inflammation and metabolic regulation. The markers assessed included C-reactive protein (CRP), tumour necrosis factor-α (TNF-α), various interleukins, and monocyte chemoattractant protein-1 (MCP1). Additionally, the researchers examined metabolic regulators such as fatty acid binding protein-4 (FABP4), growth differentiation factor-15 (GDF-15), and a suite of adipokines including total adiponectin, leptin, resistin, chemerin, vaspin, and cathepsin-S. The primary objective was to determine if these markers differed by PCOS status and if they influenced the relationship between PCOS and maternal or neonatal health outcomes.
Key Findings: Inflammation and Metabolic Regulation
The results of the study provide a nuanced view of the inflammatory state in early PCOS pregnancy. Among the wide array of biomarkers tested, only two—MCP1 and FABP4—showed significant differences based on PCOS status.
The Role of MCP1 (Monocyte Chemoattractant Protein-1)
MCP1 is a key chemokine involved in the recruitment of monocytes to sites of inflammation and is a known marker of adipose tissue inflammation. The study found that MCP1 concentrations were 15% higher in women with PCOS compared to those without (geometric mean ratio [GMR]: 1.15; 95% CI: 1.01, 1.31; p=0.04). However, this association lost statistical significance after the researchers adjusted for maternal age and BMI. This suggests that the increased MCP1 seen in PCOS is not a unique feature of the syndrome itself during pregnancy but is instead a reflection of the higher adiposity often associated with the condition.
FABP4: A Potential Link Between Adiposity and Insulin Resistance
FABP4, a protein predominantly expressed in adipocytes and macrophages, plays a critical role in lipid transport and is closely linked to insulin resistance and the development of metabolic syndrome. In this study, FABP4 concentrations were 32% higher in the PCOS group (GMR: 1.32; 95% CI: 1.04, 1.68; p=0.02). Interestingly, while the association remained significant after adjusting for maternal age, it was attenuated and became non-significant once BMI was factored into the model. This reinforces the concept that the metabolic disturbances observed in pregnant women with PCOS are heavily contingent upon their weight status at the time of conception.
The Confounding Influence of Maternal BMI
One of the most significant takeaways from this research is the degree to which maternal BMI overshadows the PCOS diagnosis in determining inflammatory and metabolic profiles. While PCOS is inherently associated with metabolic dysfunction, the “inflammatory signature” of the disease in early pregnancy appears to be largely driven by the volume and activity of adipose tissue. In this cohort, other classic markers of inflammation like CRP and TNF-α did not differ significantly between the groups, suggesting that the systemic inflammatory burden in PCOS may not be as distinct from obesity-related inflammation as previously hypothesized.
Furthermore, the study found no evidence that MCP1 or FABP4 concentrations interacted with maternal or neonatal outcomes. This means that while these markers are elevated, they did not directly predict which women would develop complications like GDM or which neonates would experience adverse events. This finding challenges the utility of using these specific biomarkers as independent screening tools for pregnancy risk in the PCOS population.
Expert Commentary: Clinical Implications
The results of this study have important implications for the clinical management of PCOS. For years, clinicians have wondered if the increased pregnancy risks in PCOS are due to the hormonal environment of the syndrome (such as hyperandrogenism) or the metabolic environment (such as obesity and insulin resistance). By demonstrating that BMI is the primary driver of MCP1 and FABP4, this study points toward metabolic health and weight management as the most actionable targets for intervention.
From a mechanistic perspective, FABP4 is particularly interesting. As a protein that links obesity to systemic inflammation and insulin resistance, its elevation in PCOS—even if driven by BMI—indicates a state of metabolic stress. However, since it does not independently predict outcomes, its role may be more as a marker of existing adiposity rather than a causal agent of pregnancy complications. This aligns with current evidence-based guidelines that emphasize pre-conception counseling and lifestyle modifications to achieve a healthy BMI before pregnancy in women with PCOS.
Limitations of the study include its cross-sectional design and the fact that the subjects were already identified as being at risk for GDM, which may limit the generalizability of the findings to all women with PCOS. Larger longitudinal studies that follow women from the pre-conception period through postpartum are needed to fully map the inflammatory and metabolic trajectories associated with the syndrome.
Conclusion
In summary, while women with PCOS enter pregnancy with higher levels of certain inflammatory and metabolic biomarkers like MCP1 and FABP4, these elevations are primarily a byproduct of maternal adiposity. The study suggests that the PCOS diagnosis itself does not independently alter these specific markers once BMI is accounted for. For healthcare providers, this reinforces the critical importance of addressing weight and metabolic health in the pre-conception period. While the hunt for specific PCOS-related biomarkers continues, the current best practice remains a focus on traditional metabolic risk factors to ensure the best possible outcomes for both mother and child.
References
Alesi S, Mason T, Ellery SJ, et al. Early pregnancy biomarkers of inflammation and metabolic regulation in polycystic ovary syndrome. The Journal of Clinical Endocrinology and Metabolism. 2026. PMID: 41802911.
