Immediate vs Delayed Free-Flap Breast Reconstruction: Higher Readmission After Immediate Reconstruction in a 20,415-Patient IPTW NSQIP Cohort

Background The timing of microsurgical breast reconstruction remains a central question in oncologic care. Immediate reconstruction offers psychological and aesthetic advantages, yet concerns persist that it may increase short-term morbidity. Prior studies have been limited by selection bias and inconsistent risk adjustment, leaving the comparative safety of immediate versus delayed reconstruction unresolved at a national level. Methods We performed a retrospective cohort study of adult women undergoing free-flap breast reconstruction (CPT 19364) in the ACS–NSQIP registry (2012–2022). Covariate balance between immediate and delayed cohorts was achieved using inverse probability of treatment weighting (IPTW) with prespecified standardized mean difference thresholds < 0.1. Multivariable logistic regression and IPTW-weighted logistic regression estimated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for 30-day complications. Results A total of 20,415 patients were included (10,362 immediate; 10,053 delayed). After IPTW adjustment, immediate reconstruction demonstrated higher odds of readmission (6.4% vs. 5.1%; OR 1.35, 95% CI 1.18–1.54), perioperative transfusion (9.8% vs. 7.5%; OR 1.43, 95% CI 1.28–1.59), and unplanned return to the operating room (12.2% vs. 10.7%; OR 1.27, 95% CI 1.16–1.40). Smaller associations with superficial (OR 1.23, 95% CI 1.07–1.42) and organ/space surgical-site infection (OR 1.43, 95% CI 1.02–1.99) did not persist after correction and should be regarded as hypothesis-generating. Major systemic events—including sepsis, stroke, myocardial infarction, and cardiac arrest—were rare ( < 2%) and comparable between groups. Conclusions In this rigorously weighted national analysis to date, immediate free-flap breast reconstruction was associated with modest increases in early healthcare utilization-related complications but no excess in life-threatening events. These findings refine a longstanding clinical debate, supporting balanced patient counseling and value-oriented pathway development in microsurgical breast reconstruction.