Anthem, Cigna Privately Bicker as They Seek Merger Approval

Quarrels have broken out behind the scenes of Anthem Inc.’s $48 billion proposed acquisition of Cigna Corp. as the health insurers seek regulatory approval for their landmark deal, according to a series of letters reviewed by The Wall Street Journal.

People on both sides say the squabbles could delay or derail antitrust approvals, which are typically harder to obtain if both parties aren’t in sync. While neither company has sought to...