The average deal size of venture-backed mergers and acquisitions in the third quarter was $226.3 million, the highest level since the closing months of 2000, according to the National Venture Capital Association.

Of 67 ventured-backed M&As completed between July and September, 34 had disclosed values totaling $7.7 billion, a 104 percent from the same period last year, the trade group reported. At the same time, there were 12 initial public offerings by venture-backed businesses totaling $945.2 million, the bulk of which were in the technology sector.

Despite the gains, the exit market is expected to face challenges in the months ahead, according to Mark Heesen, the group's president. "We are hearing that acquisitions are taking longer to close as corporations remain cautious in an unpredictable market," Heesen said in a statement.  A growing number of venture-backed companies were already trading below their offering price, he added.