Amazon.com Inc. fell as much as 4 percent in Nasdaq trading after Goldman Sachs Group Inc. said the Internet retailer may miss analysts’ fourth-quarter sales estimates.

Amazon’s sales may grow 38 percent from a year earlier to $17.9 billion, less than analysts’ average estimate of $18.2 billion, Heather Bellini, an analyst at Goldman Sachs, said in a note today.

The retailer historically outpaces overall holiday e-commerce spending growth by 23 percentage points, according to the analysis. Bellini said comScore Inc. data released today show that U.S. Internet commerce rose 15 percent to $25.3 billion in the first 56 days of the holiday season.

“While the comScore numbers are just one data point which does not capture international sales or breakout individual companies’ sales, taken alone they seem to suggest the potential for downside risk to consensus forecasts” for the fourth quarter, Bellini wrote.

Amazon fell 1.7 percent to $170.89 at 11:10 a.m. New York time, and traded as low as $166.97. The shares had declined 3.4 percent this year before today.

Separately, Amazon said it sold “well over” 1 million Kindles a week in December, with record demand led by its Kindle Fire tablet.

The top three sellers on Amazon’s website were the Kindle Fire and two electronic readers, the Kindle Touch and Kindle, Seattle-based Amazon said today in a statement. Gifting of Kindle books rose 175 percent from a year earlier in the period from Nov. 25 to Christmas Day, Amazon said without providing sales data.

The company introduced the Kindle Fire, which has a 7-inch display and sells for less than half the price of Apple Inc.’s least-expensive iPad, on Sept. 28 in a bid to erode Apple’s dominance. Amazon is releasing a Fire update to improve performance, make touch navigation easier and let users choose what items are displayed, after some users complained.