After mergers and acquisitions activity boomed in 2018 to the tune of $3.53 trillion in total deals, nearly half of which were credited to the United States alone ($1.5 trillion), market watchers could fairly place big expectations on this year’s output. Not only was last year an unqualified success, but it came on the heels of a strong 2017 ($1.3 trillion in U.S. M&A), and not long after the biggest year on record (2015’s total was nearly $1.8 trillion).

But optimism must still be guarded. A number of adverse market trends and developments could put a damper on M&A activity in 2019 and beyond.