Just as private equity-backed acquisitions are gaining steam, the Federal Trade Commission's new review process for reviewing proposed mergers risks slowing slowing down some PE deals and halting others in their tracks.

Under the revised Hart-Scott-Rodino premerger notification rules, companies will have to provide a mountain of additional information, some time-consuming to collect—creating a larger data trove for regulators to draw from to support steering deals out of the fast lane and into full, antitrust investigations.