It's high time for legal departments to adapt to the increasingly complex and global nature of mergers and acquisitions, which are taking longer than ever to finalize, according to a new study. 

Today's M&A deal now drags on for an average of 38 days before closing—31% longer than the average in 2010, according to global research and advisory firm Gartner Inc.  

The wait is even more pronounced for midsize deals of $500 million to $5 billion and large deals of more than $25 billion, which now take an average of 106 and 279 days to finalize, respectively. 

An analysis of 23,000 transactions involving S&P companies in the past decade shows that M&A deals have become more complex, data-driven and often involve cross-border issues, according to the report. Those factors, coupled with new data regulations and compliance concerns, appear to be behind the M&A slowdown. 

Mike Slipsky, a partner at Poyner Spruill in Raleigh, North Carolina, who focuses on M&A deals and reviewed the report, also suggested that the trend could be due, in part, to the availability of new tools that allow less sophisticated or smaller parties in transactions to access "really granular data" during a deal.  

"And the upshot of that is that there are probably better-informed parties, particularly on the sell side," he said. "Before, they might not have known what they were agreeing to. This might be where greater availability of data has leveled the playing field a little bit."

So what can legal departments do to respond to the increasingly complex and global M&A landscape? 

Expansion is one idea. Increasing in-house legal capacity makes sense for companies that are looking to handle high-volume acquisitions, according to Abbott Martin, vice president and research leader for Gartner's legal practice. 

In-house leaders and firms also could develop more "agile deal teams" that can use subject matter experts more efficiently than traditional, static deal teams that work with limited or fixed expertise, the report states.

"From an in-house perspective, you can't be an expert in everything, and that's why you have outside experts. But trying to understand the lay of the land and staying on top of recent developments would be a good idea," Slipsky said. 

"And, as a practical suggestion, try establishing relationships with outside experts so they can be brought in early, particularly if you know the target company is in a data-centric business or in a highly regulated industry like health care or banking," he added. 

The report further recommends that legal departments beef up M&A due diligence related to cybersecurity and data protection, and adhere to a "compelling deal narrative" that is focused on the reason for the transaction and its value.

Mike DeFranco, chair of Baker McKenzie's global M&A practice group, said legal departments for companies that are beginning to eye tech-related acquisitions need to be prepared to talk with their firm's business teams about how those deals will be different from the transactions that they've done historically.

"We have a number of industrial companies that are buying tech and may even be buying startups for the first time," he said. "They may be focusing on issues that they haven't had to focus on in the past," such as intellectual property and patent matters. 

Meanwhile, Baker McKenzie is predicting in its latest global transactions forecast that there will be a "slowing of the transactions pipeline" next year as M&A volume drops 25% globally. But the firm also anticipates that initial public offerings will rise in total value from $152 billion this year to $215 billion, due in large part to the expected Saudi Aramco initial bond offering. 

The report states that "IPO pipelines are healthy and some firms may look to accelerate their flotation plans, fearing a renewed slump in equity prices." 

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