Earnings have been doing the heavy lifting for much of the recent rally. Continued growth may be one of the only ways to keep it going, even at the expense of stock valuations.

Although stocks have had a difficult few weeks, it was just a month ago that the S&P 500 closed at a new all-time high, and it's still up more than 11% since the start of the year. The index, although slightly cheaper than it was, trades around 21 times forward earnings, meaning a lot has to go right to support that multiple. Meanwhile, worries are piling up-from increasing oil prices to ongoing tariff headwinds and the volatile artificial intelligence trade.

Higher yields, major initial public offerings, and slower earnings-per-share growth, however, remain the three most significant risks to valuations today, according to BCA Research Head of Equities Noah Weisberger in a note Monday. He reiterated his year-end S&P 500 estimate of 8,100, but warned that "the path to our year-end target increasingly dependent on earnings."

The problem of higher yields remains a tricky one. This week's Federal Open Market Committee meeting follows follows inflation readings that remained stubbornly high. The data "did not make the Federal Reserve's job any easier," as Scott Ellis, managing director of corporate credit at Penn Mutual Asset Management, puts it.

That's because odds of an interest rate hike increased after last week's readings, even as President Donald Trump continued to argue for a cut, saying on Sunday that the U.S. should have the world's lowest interest rates. For now, investors are betting on an increase, as "services inflation and a stable labor market may strengthen the Fed's conviction that additional tightening is needed to return inflation to target," write strategists at Glenmede.

If nothing else, however, this week's FOMC meeting will at least provide clarity, which Weisberger thinks will ease investor worries, particularly as a rate hike need not be a "death knell for equities, to the extent that it reflects a firm business cycle and growing investment demand, even if higher yields are a valuation headwind."

Likewise, although the big AI IPO dates are somewhat of a moving target-and there's no systematic evidence that big IPO waves reliably come just before market peaks-Weisberger is concerned that they're another problem for stock valuations.

A pattern has emerged over the past three decades showing that below-average returns-including negative ones-tend to follow periods that are in the top quintile for IPO issuance. "The valuation risk is even more acute: when IPO activity is in the top two quintiles, P/Es tend to compress on a forward basis," he writes.

Ed Yardeni, president and chief investment strategist at Yardeni Research, is more blunt: "Investors do not have unlimited capital. If several mega offerings arrive within a short period, institutions may have to sell existing holdings to make room."

That brings everything back to earnings as potentially the only real way to buoy valuations from here.

On the one hand, bulls may point to the fact that earnings growth has been exceptionally strong-with profits growing at double-digit rates in recent quarters. On the other, that only increases the pressure to keep the party going. History shows the strongest returns occur when earnings per share growth is high and rising, but returns are weaker when high earnings growth is slowing, Weisberger notes.

Nonetheless, slowing growth doesn't necessarily torpedo returns if it's a transition to more sustainable profit levels, and his base case is that earnings growth successfully walks that tightrope-strong enough to support more measured but still positive stock returns even as slower growth acts as a minor drag on multiples.

"That said, the path forward is necessarily narrow," he warns, particularly if that slowing intensifies. "We will be keeping a careful eye on revisions, guidance and surprises particularly in the dominant Technology sector, for signs that slowing EPS growth is presaging something worse. But for now, the market can likely live with some multiple compression as long as earnings growth remains robust."

In earnings we trust.