Amazon (NasdaqGS: AMZN) will likely guide the action in retail exchange traded funds (ETFs) on Wednesday after the company reported quarterly earnings that missed expectations.

Amazon shares weakened in after-hours trading Tuesday following the earnings release as investors worried about the company’s lower operating margin in the first quarter.

Profit margin has been a concern recently for Amazon “because of higher spending to expand into different product offerings and support the growth of the business,” said BWS Financial in an earnings outlook.

On the conference call Tuesday, Amazon executives continued to talk enthusiastically about the Kindle e-book business.