Limited impact of body mass index on the risk of postoperative complications after implant-based breast reconstruction: A retrospective cohort study of 1847 patients

BACKGROUND: High body mass index (BMI) has been linked to higher risk of complications following implant-based breast reconstruction. However, the impact of increasing BMI within the normal to overweight range (18.5-30 kg/m2) remains underexplored. We aimed to examine the association between BMI and complications and evaluate differences in risk of implant loss between patients undergoing immediate- and delayed reconstruction.

METHODS: Consecutive patients who underwent implant-based breast reconstruction from 2010-2023 at three plastic surgical departments were analyzed with BMI as a continuous variable. The primary outcome was implant loss stratified by immediate versus delayed reconstruction. Secondary outcomes included implant infection, seroma, hematoma, and mastectomy skin flap necrosis. All outcomes were analyzed with multivariate Cox regression.

RESULTS: We included 1847 patients (2631 breasts) with a median BMI of 23.3 kg/m2 (IQR 21.0-25.8, range 17.1-36.9). In patients undergoing immediate reconstruction, BMI was significantly associated with an increased risk of implant loss (P=0.04) but not after delayed reconstruction (P=0.22). Overall, higher BMI was significantly associated with risk of implant infection (P=0.003) and seroma (P<0.001) but not hematoma or mastectomy skin flap necrosis. The absolute risk difference for implant loss between BMI 23 kg/m² (6.2%) and 30 kg/m² (8.2%) was 2.0% (95% CI -2.9 to 6.8) for immediate reconstruction.

CONCLUSION: The small absolute risk differences for complications in patients with BMI between 23 and 30 kg/m² suggest that patients with BMI ≤30 kg/m² should not be discouraged from implant-based breast reconstruction. However, delayed reconstruction may be a safer option for patients with higher BMI.