September was a wild month in the markets, and many stocks endured big declines. Interest rate hikes and global macroeconomic conditions put downward pressure on the market, and a handful of companies compounded those challenges with disappointing earnings reports. These high-profile stocks experienced huge moves and illustrated important trends that drove the market in September.

1. MongoDB

Mongo DB (MDB -2.15%) endured a tough start to the month after publishing earnings late in August. It continued to flounder along with the rest of the market as growth stocks -- represented by the Vanguard Growth ETF below -- took a beating throughout September.

MDB Chart

Data by YCharts.

The company's quarterly report wasn't particularly bad. Revenue grew more than 50% year over year, and its gross margin expanded to 71%. MongoDB posted better-than-expected results for both sales and net losses in its fiscal second quarter. However, the company's outlook and commentary didn't sit well with investors. Its guidance for the current quarter was slightly below analyst forecasts, implying a slowdown. There's growing concern that a challenging economic environment will impact MongoDB's ability to expand its relationship with existing customers, which is a major threat to growth.

This is a clear demonstration of multiple important stock market themes. MongoDB offers an innovative platform that is essential to software development functions for nearly 40,000 businesses, and it's growing at a faster pace than the vast majority of stocks. Despite that, the mere threat that growth might decelerate resulted in a huge sell-off. MongoDB is still burning cash to support its expansion, and the stock is fairly expensive -- its price-to-sales ratio was above 18 at the start of September.

Investor risk appetite must remain high to support expensive valuations for growth stocks. Investors are responding to rate hikes by pulling capital out of the stock market, and uncertainty around MongoDB's medium-term prospects wound up slamming the stock. It's hard to argue the company should lose more than a third of its value due to the latest quarterly report, but that's just how growth stock investing works sometimes. Long-term investors now have an opportunity to buy in at more attractive valuations, which is a common theme among tech stocks right now.

A person rests their forehead in their hands while looking at a laptop.

Image source: Getty Images.

2. FedEx

FedEx (FDX -0.79%) is an established bellwether stock that was crushed after it published an ominous business update. The company released an early look at its fiscal 2023 first-quarter earnings with warnings of significant volume declines. It noted particular weakness in Asia and Europe due to macroeconomic headwinds, which is worrisome, because the North American economy is also facing a potential slowdown over the next few quarters. The company expected to miss Wall Street's estimates by a wide margin, and that news caused the stock to drop more than 20% overnight.

FedEx is a $40 billion business with diversified, global operations and a wide economic moat. It's remarkable to see a quarter of its value wiped out so quickly, especially because it's a blue-chip stock that pays a dividend -- this isn't some growth stock with a lofty valuation.

This is all a clear indication that global macroeconomic headwinds are quite serious. This also shows just how much risk was created by the COVID-19 bull market, which was fueled by low interest rates and federal stimulus. FedEx is now trading at the same ratio of enterprise value to earnings before interest, taxes, depreciation, and amortization (EBITDA) that it had in 2014, so it's not unfathomably cheap.

FDX EV to EBITDA Chart

Data by YCharts.

Central banks around the world are raising interest rates to fight inflation. This is pulling capital away from stock markets, and it's weighing on global economic activity. This sell-off may have captured most of the downside FedEx will endure through this market cycle, but it's going to be a while until there's any major catalyst for growth.

FedEx is considered a bellwether, because data on shipping and freight provides some evidence on the level of overall business activity. The current market downturn isn't limited to growth stocks, and investors shouldn't be shocked to see losses among mature blue-chip stocks. Stocks from the business services and industrials sectors could be especially at risk.

3. Nike

Nike (NKE -0.23%) tumbled 13% after releasing its fiscal first-quarter results on Sept. 29. The company topped Wall Street estimates by growing revenue 4% year over year, and it also produced higher-than-expected profits. However, investors were dismayed by a contracting gross margin and a huge increase in Nike's inventory on the balance sheet. Both are potential early indicators of weak demand and falling consumer sentiment.

Consumer spending data has remained decent in recent months, even as high inflation has affected many households. The looming impacts of a recession are also likely to weigh on consumer spending, and that's especially true if unemployment spikes higher.

There have already been numerous warning signs that business-to-business companies are entering a weak period, bringing more scrutiny on consumer stocks too. As interest rates rise, pay attention to employment and consumer spending data. These will be important indicators for economic activity and stock market performance.