Investors have been priming themselves for a potentially huge influx of companies selling stock to the public for the first time, led by ridesharing game changers Uber and Lyft, but the outlook is more uncertain with the vicious return of volatility to the market.

For companies trying to raise capital, volatility is the enemy.

"We enter 2019 on uncertain footing," said Renaissance Capital, a research firm focused on initial public offerings (IPO).

The market is coming off an outstanding 2018 for stock offers, with 231 companies going public and raising 61 billion U.S. dollars, the best year since 2014 when Alibaba entered Wall Street, according to Dealogic.

But financial markets have been on a roller-coaster of late, generating questions about whether conditions are right for more IPOs.

Angst over higher Federal Reserve interest rates and projections for slower global growth have been the key factors behind the swoon in December by a market already unnerved by escalating trade tensions.

IPO activity through the first 10 months of 2018 topped 2017 levels by 42 percent, but tumbled 66 percent in the final two months of the year as stock markets gyrated.

Several offerings that planned for the end of the year were pushed into 2019, according to a person with a major exchange.

Volatility is "definitely a priority in terms of IPO conversations," said this exchange source.

Too much volatility?

Waiting in the wings and expected to launch in 2019 are several prominent "unicorns" - a private company worth more than one billion U.S. dollars.

This group includes ridesharing service Lyft, which filed confidential papers to go public, and its arch rival Uber, according to US business press.

Others that are expected to go public include the lodging service Airbnb, messaging service Slack, content website Pinterest and data analytics company Palantir.

Market specialists are confident these firms should be better equipped to navigate the more challenging environment given their size.

"Volatility is one of the key factors when companies plan for their IPOs," said Jeff Thomas, who supervises introductions of IPOs at Nasdaq.

Companies have even been known to accelerate a plan to go public if they anticipate even greater volatility down the road.

Still, the market turmoil could affect how much money companies raise.

"If current market conditions presage a US economic slowdown in 2019, investors may want to haircut valuations to incorporate slower earnings growth," said Nicholas Colas, co-founder of DataTrek Research, who noted that Uber, Lyft and Airbnb are all dependent on consumer spending, while Slack and Palantir rely on corporate spending.

"None have been tested by a US recession in their current forms," Colas said.

"Bankers and lawyers are definitely aware" of the spike in volatility, said Douglas Ellenoff, a securities attorney. But stock market jitters won't derail offerings as long as it is "moderate."