OBJECTIVES: Breast cancer patients after receiving mastectomy can undergo immediate breast reconstructions (IBR), or wait months later and undergo delayed breast reconstructions (DBR), depending on physicians’ evaluation, patients’ preference, and types of BR. Current guidelines were inconclusive regarding the timings of BR because of the inconsistent evidence about post-operative complications. Recent studies showed that IBR gradually replaced DBR because of surgical improvements. Yet, there is a need to continuously evaluate complications associated with DBR to justify recommendations. The objective of this study is to assess the relationship between complications and the timing of procedures controlling for types of BR. METHODS: A retrospective cohort of 13,257 women underwent BR was identified from 2009 National Inpatient Sample. Patients were grouped into 1) DBR if she underwent BR alone or 2) IBR if underwent mastectomy and BR during the same hospitalization. Complications included, for example, wound complications, infection, hematoma, fat necrosis (identified by ICD-9 procedures and diagnoses) and complications related to the device, surgical procedure, and medical care (identified by HCUP CCS diagnoses). To control for patient and hospital characteristics and BR types, a multivariate analysis was conducted. RESULTS: Of all the inpatient BR visits, 50.3% were for DBR. About 46.7% versus 14.8% of women who received DBR versus IBR experienced complications respectively. The differences in complication rates were most pronounced for women who received implant reconstructions (64.2% versus 10.1% for DBR versus IBR). Women who received DBR were about 7.6 times more likely to have infections (18.5% versus 2.4% for DBR versus IBR). After adjusting for covariates, women who underwent DBR were significantly more likely to have complications (P<0.0001). For women underwent DBR, the odds of experiencing complications were 1.2-19.9 higher than the odds for women underwent IBR, depending on the BR approach. CONCLUSIONS: Complications were significantly higher among women who underwent DBR and the complication rates varied by the BR approach.