University of Chicago Medicine has acquired a controlling interest in four west suburban hospitals, expanding the health system’s footprint in Illinois.

University of Chicago Medicine now owns a chunk of AdventHealth’s Great Lakes Region, which includes four hospitals in Bolingbrook, Glendale Heights, Hinsdale and La Grange, as well as a network of nearly 50 physicians’ offices and outpatient sites.

Those four hospitals and other west suburban sites will now include in their names the title UChicago Medicine AdventHealth. AdventHealth still owns part of the hospitals and will continue to manage daily operations.

The new arrangement became official Jan. 1, and was announced in September. Financial terms of the deal are not being disclosed.

Hospital systems leaders say the deal will give AdventHealth patients better access to UChicago Medicine specialists and clinical trials, closer to home, and it will give UChicago Medicine patients who live in the west suburbs more care options in their own communities.

The four west suburban hospitals were previously part of Amita Health, which was a partnership between AdventHealth and Ascension, before those two systems unwound the partnership last year.

The acquisition is UChicago Medicine’s latest move to grow and reach farther into the suburbs. The system, which includes University of Chicago Medical Center, acquired Ingalls Memorial Hospital in Harvey in 2016 and broke ground in August on a 130,000-square-foot medical facility in Crown Point, Indiana.

In February, UChicago Medicine announced plans to build a $633 million, 500,000-square-foot cancer hospital in Hyde Park to address health inequities on the South Side and draw patients from across the region.

It’s common for health systems to grow by acquiring other hospitals in the area. Hospital leaders say the deals help them gain economies of scale, reach more patients and adapt to changing technologies. Hospitals often say they hope to improve care and affordability by merging, though mergers and acquisitions also often increase hospitals’ bargaining power with insurers, allowing them to charge higher rates for services.

AdventHealth is affiliated with the Seventh-day Adventist Church and has more than 50 hospitals and hundreds of care sites in nine states. Only its Great Lakes Region was involved in the deal with UChicago Medicine.