UnitedHealth may have been among the medical insurers who feared the rising medical care costs and increased liability expected from implementation of the Affordable Care Act, but the nation’s largest insurer cited “sales to individuals and smaller employer groups” as a contributor to its enrollment growth at the end of 2013. The company added 4.5 million customers in total last year and its revenues increased 10.7% with help from a 26% revenue bump for Optum — UnitedHealth’s technology services arm. In what might be an unintentional boost from the ACA, Optum runs the unit that was brought in to help repair HealthCare.gov in the wake of the government insurance site’s disastrous rollout.