Apple (AAPL -1.10%) just dropped its fiscal fourth-quarter update -- and it was packed with interesting takeaways. Just to list a few nuggets from the report, revenue increased 20% year over year, earnings per share soared 41%, iPhone revenue jumped 29%, and services revenue nearly hit $10 billion. 

But there were plenty more insights to be had for investors who went beyond Apple's fourth-quarter earnings release and tuned into the company's conference call on Thursday evening. Notable tidbits from the call included a closer look at management's weaker-than-expected first-quarter guidance, an update on Apple's thriving wearables business, and more.

Apple Watch Series 4

Apple Watch Series 4. Image source: Apple.

Apple's wearables business is surging

Revenue from Apple's wearables devices (Apple Watch, AirPods, and Beats products), skyrocketed in Q4, rising 50% year over year. Strong performance from wearables helped Apple's Other Products segment's revenue rise 31% year over year to $4.2 billion.

With so much momentum in wearables, CFO Luca Maestri said Apple is renaming its other products segment to explicitly call out wearables.

[S]tarting with the December quarter, we will be renaming the Other Products category to wearables, home, and accessories to provide a more accurate description of the items that are included in this product category.

About Apple's decision to no longer report unit sales

One takeaway from Apple's earnings call that surprised investors was management's decision to stop reporting unit sales data for the iPhone, iPad, and Mac beginning with its first quarter of fiscal year 2019. Some investors may worry that the company's decision to hide this data from investors reflects a bearish outlook from management on the key metric. But Maestri argued the metric simply isn't as relevant to the company's business performance as it was in the past.

As demonstrated by our financial performance in recent years, the number of units sold in any 90-day period is not necessarily representative of the underlying strength of our business. Furthermore a unit of sale is less relevant for us today than it was in the past given the breadth of our portfolio and the wider sales price dispersion within any given product line.

What about Apple's guidance?

Apple's outlook for fiscal first-quarter revenue to come in between $89 billion and $93 billion fell below a consensus analyst estimate for first-quarter revenue of $93.02 billion. In addition, this guidance notably implied a much slower growth rate than what the tech giant has been serving investors recently. Apple capped off 2018 with its eighth quarter in a row of accelerating revenue growth, growing fiscal fourth-quarter revenue by 20% year over year. But Apple's guidance for its fiscal first-quarter revenue implies just 1% to 5% year-over-year growth.

Why the expected slowdown? Maestri listed the factors driving this guidance in the company's earnings call:

  1. This year, Apple launched its high-end new iPhones in late Q4 and its more affordable new iPhones in Q1 -- the reverse of last year.
  2. Maestri expects $2 billion of foreign exchange headwinds.
  3. Though Apple is confident about its reinvigorated product lineup headed into the holidays, management has "uncertainty around supply and demand balance."
  4. Apple is facing macroeconomic uncertainty in some emerging markets.

Investors shouldn't fret management's expectations for slower growth too much. Not only has Apple's guidance for the holiday period often proven to be conservative, but management's forecast for slower first-quarter growth doesn't take away from the incredible growth Apple has delivered recently. In 2018, Apple's top line increased by a whopping $36.4 billion compared to 2017. Clearly, Apple's business is seeing some considerable momentum.