High basal serum oxytocin cuts IVF live birth rates; elevated follicular fluid oxytocin improves ovarian response.
Background
Achieving successful live birth rates in In Vitro Fertilization (IVF) cycles remains a significant challenge for infertile couples. While oxytocin is well-known for its role in labor and social bonding, its precise involvement in early reproductive processes, particularly during ovarian stimulation and embryo transfer, is less understood. Current IVF protocols often focus on optimizing ovarian stimulation and endometrial receptivity, but endogenous hormonal factors like oxytocin could play a critical, yet overlooked, role. Understanding these associations could provide novel biomarkers or therapeutic targets to improve IVF outcomes.
Study Design
This prospective cohort study enrolled 680 infertile patients undergoing IVF cycles between October 2024 and January 2025. Researchers measured endogenous oxytocin levels in both serum (basal, prior to ovarian stimulation) and follicular fluid. The associations between these oxytocin levels and live birth rate (LBR) were analyzed using multivariable logistic regression, inverse probability weighting, and a double robust model. Smoothed curve fitting explored non-linear relationships, and Spearman correlation examined links with clinical parameters.
Results
Serum oxytocin exhibited a negative linear association with LBR (p-nonlinear = 0.911), while follicular fluid oxytocin showed a positive association (p-nonlinear = 0.425). The double robust model provided specific quantitative insights: > Each 100 pg/mL increase in basal serum oxytocin decreased the likelihood of live birth by 37% (95% CI: 25%-47%). Conversely, a corresponding 100 pg/mL increase in follicular fluid oxytocin improved the likelihood of live birth by 18% (95% CI: 2%-37%). Additionally, serum oxytocin correlated positively with triglycerides (r = 0.294), LDL-C (r = 0.165), and insulin (r = 0.257), but negatively with HDL-C (r = -0.167). Follicular fluid oxytocin, however, correlated positively with favorable ovarian response markers, including hCG-trigger day estradiol (r = 0.229) and the number of oocytes retrieved (r = 0.248).
Why It Matters
This study highlights the dual and contrasting roles of oxytocin in IVF success, suggesting that its levels could serve as a valuable biomarker for IVF prognosis. For clinicians and patients, basal serum oxytocin measurement prior to ovarian stimulation could help identify individuals at higher risk of lower live birth rates, potentially guiding personalized treatment strategies or counseling. While not a direct intervention, these findings open avenues for future research into modulating oxytocin pathways or addressing associated metabolic factors to improve IVF outcomes. Optimizing endogenous oxytocin levels, or understanding their implications, could become a new frontier in fertility treatment, moving beyond traditional metrics.