Does ovarian stimulation accelerate the progression of BI-RADS categories? a propensity score matching-based retrospective cohort study.

Purpose: To investigate whether controlled ovarian stimulation (COS), as part of assisted reproductive technology (ART), accelerates the progression of BI-RADS categories. Methods: This was a single-center, retrospective, propensity score matching (PSM) cohort study conducted from January 2020 to January 2025. A total of 9, 632 women were initially enrolled. After 1:1 PSM, the final analyzed cohort comprised 229 pairs of women aged <35 years (younger group) and 154 pairs of women aged ≥35 years (older group). The exposed group comprised women who underwent COS for IVF/ICSI treatment, while the control group consisted of women who underwent routine physical examinations during the same period with no history of ART treatment. The primary outcome was the change (escalation or regression) in BI-RADS category from baseline to follow-up (≥12 months), blindly re-evaluated by two senior sonographers. Propensity score matching was performed to balance baseline characteristics between groups, and subgroup and trend analyses were conducted. Results: After PSM, baseline characteristics were well balanced between the groups. In the <35 years cohort, the exposed group showed significantly higher rates of both BI-RADS category escalation (30.13% vs. 13.54%, P = 0.019) and regression (14.84% vs. 6.98%, P = 0.007) compared with the control group. In the ≥35 years cohort, the escalation rate was significantly higher in the exposed group than in the control group (36.36% vs. 12.33%, P<0.001), whereas no significant difference was observed in regression rates. Trend analysis revealed that among women aged ≥35 years, the risk of BI-RADS category escalation increased significantly with the number of stimulation cycles (trend P = 0.04). All 12 patients who underwent biopsy due to escalation to BI-RADS 4A had benign pathological findings. Regarding pregnancy outcomes, the <35 years group demonstrated significantly higher clinical pregnancy and live birth rates, as well as a lower miscarriage rate, compared with the ≥35 years group. Conclusion: COS is associated with an increased short-term risk of BI-RADS category progression, particularly among women aged ≥35 years. However, it is crucial to note that all 12 patients who underwent biopsy following an upgrade to BI-RADS 4A had benign pathological findings. This suggests that the observed imaging changes may represent a transient, hormone-driven breast tissue response rather than an indicator of malignant transformation. The higher regression rate observed in younger women in the exposed group may be related to subsequent pregnancy and lactation, but this remains speculative. These findings highlight the importance of age-stratified imaging surveillance during ART, rather than implying an elevated risk of breast cancer. Long-term prospective studies are warranted to validate these observations.