OBJECTIVES: Contraceptive methods vary by effectiveness, duration of effect and product-related costs. Consideration of both product- and unintended pregnancy (UP)-related costs over the full duration of effect is vital when health care payers make contraceptive coverage decisions. This analysis aimed to estimate the medical and pharmacy budget impact to a US health care plan when switching women from short-acting reversible contraceptives (SARC) to a low-dose levonorgestrel intrauterine system (LNG-IUS-12). METHODS: A three-year budget impact model was developed to estimate costs before and after availability of LNG-IUS-12, among women aged 15-44 years, at risk of UP, and covered by a US health care plan. US Census and National Survey of Family Growth determined current contraceptive usage. Pregnancy outcomes and failure rates were estimated using published literature. The model considered costs of contraceptives derived from Wolters Kluwers Health-MediSpan Master Drug Database, physician visits from Medicare Reimbursement Rate and pregnancy outcomes (live birth, induced or spontaneous abortion, and ectopic pregnancy) from the Health Care Utilization Project. Consistent with the Health and Human Services mandate on preventive services, no patient co-pay, co-insurance, or deductible was factored into this analysis. LNG-IUS-12 was assumed to gain 0.5%, 0.3% and 0.2% market share from SARC methods in years 1, 2 and 3 respectively, resulting in a target cumulative 1% uptake of the contraceptive market by year 3. A potential 20% discontinuation rate for LNG-IUS-12 in the 1st year was considered. Base case model outputs were total cost, cost per member per month (PMPM) and number of UP. RESULTS: In a hypothetical cohort of 1 million plan members, the model estimated reductions of $460,552USD in total costs, $0.03USD in PMPM costs, and 119 in UP. CONCLUSIONS: Switching SARC method users to LNG-IUS-12 in a US health care plan may result in fewer UP and an overall cost savings to the plan.