More states are passing laws requiring that their attorney general or another regulator conduct premerger antitrust reviews of health care transactions, creating a new headache for dealmakers already facing stepped-up antitrust scrutiny at the federal level.

Health care attorneys say that as a result of the new state hurdles, legal departments should expect deals may take longer and be more costly to close. And in a worst-case scenario, “you may see deals fall apart if they drag out,” said April Schweitzer, a partner in the health care practice at Nixon Peabody in Chicago.