The company has invested heavily in attracting mobile shoppers: Its app is specifically designed for one-handed use (leaving the other hand free for baby) and a customer’s shopping cart stays connected to his or her account throughout the browsing process, even when bouncing between a laptop and a smartphone. (The app’s reviews section is awash in references to shopping while mothering: “Lifesaver! Last week I placed an order with one hand while holding my newborn and my 2 year old ran around,” one user wrote.)

In other words, Diapers.com is already doing business in the environment that other retailers will inevitably enter, which is probably one of the factors Amazon considered when it bought Diapers.com—and its family of sites, including Soap.com and AfterSchool.com—for $550 million in 2010. (Though the sites operate independently from Amazon, they share backend resources: Diapers.com has access to Amazon warehouses, software, and other processes—plus the sites swap data about their customers, though Geller declined to elaborate on exactly what gets shared.)

Shoppers in the United States still do most of their online shopping by laptop or desktop, according to a May report by the venture capital firm Kleiner Perkins Caufield Byers. Only about 15 percent of online shopping is done on mobile devices. But that number is expected to increase dramatically as two other changes take place: Overall time spent online continues to grow, and time spent browsing on mobile overtakes time spent browsing on desktops and laptops. Some of what Diapers.com has already learned about mobile shopping is surprising, and perhaps hints at more of what's to come. For example:

Mobile customers who shop in the wee hours (between midnight and 5 a.m.) spend a much longer time shopping than their daytime counterparts. Night owls were more likely to browse than buy, and their sessions were 30 percent longer than those who shopped between 5 a.m. and 5 p.m.



Mobile shopping is mostly happening from home or at work rather than on the go. Some 75 percent of mobile shopping takes place over wifi networks rather than data networks, spokespeople told me. “Many of our customers cite that they place orders on their Diapers.com app while rocking or nursing their baby,” Geller said.



Smartphone use is going up as tablet use is going down. In the past year, the percentage of total orders on Diapers.com coming from tablets has “decreased significantly” despite the overall growth in mobile, Geller said.

“The modern mom—I see it from my wife and from my wife’s friends—the phone has become such a useful tool to have at her side and in her pocket and in her hand,” Geller said. “We’re going to continue to see growth in that area. We absolutely believe that the phone is mom’s co-pilot to some degree. To the extent that we want to be her best friend, we see those things go hand in hand.”

Diapers.com sees mothers as its core shoppers. Which makes sense: New mothers, especially, are thought to be a key demographic for brands that want to establish loyalty. Early parenthood is one of a few times in life when people find themselves evaluating new products that they’ll potentially continue to buy (often in bulk) for years. And once that brand loyalty is set, it can be hard to shake: People who buy Tide laundry detergent, for instance, named it as one of the few brands they refused to switch out for a cheaper generic alternative during the recession, one survey showed. (Coca-Cola was another.)