"Moms are at the center of their family's offline life, so it's little surprise that they're also at the center of many of the biggest trends online as well," Nielsen wrote in its report. "Whether to look up the latest product reviews or to connect with friends, families and even brands through social networks, American moms are particularly active and influential online."

Pinterest Reigns

American moms are clearly showing favorites when it comes to family and lifestyle sites. In a ranking of the top five sites in this category, 4.9 million moms choose Pinterest, 4.8 million choose Disney Online, 4.4 million go to iVillage Network, 4.2 million opt for WebMD, and 3.8 million go to Everyday Health.

What about the top five social networks and blogs for moms? No big surprises here, but Nielsen did quantify it. More than 72 percent of moms in Nielsen's survey rank Facebook first (27.9 million). Three out of four American moms visited Facebook in March 2012.

Facebook is followed by 24.3 percent who listed Blogger. Twitter, WordPress and Tumblr round out the top-five list. About one in three bloggers are moms and 52 percent of those bloggers are parents with kids under 18 in the household. Another 50 percent of moms actively participate in social-media access platforms via social-media devices. That compares with 37 percent of the overall general population.

Implications for Advertisers

"Moms who blog are more than twice as likely to follow brands and celebrities compared to the online average," Nielsen reported. "To help save time and money, many moms shop online; moms are 35 percent more likely to shop for clothes, 50 percent more likely to buy toys, 29 percent more likely to buy music, and 23 percent more likely to purchase e-books online within the past 30 days."

We caught up with Rob Enderle, principal analyst at the Enderle Group, to discuss why moms are so digitally connected and what these numbers potentially mean for online -- and mobile -- advertisers. Generation after generation, he told us, women have been the most networked and socially engaged members of the family so it makes sense that moms would gravitate toward these sites and tools.

"Guys tend to move toward new technology tools faster than women. But this is one of those cases where technology tools are in fact becoming very popular with women, which is a traditional group that is underserved," Enderle said.

"This suggests that a large portion of the audience, perhaps the major portion of the audience, is women. Advertisers almost always assume that with regard to a technology type display medium that guys are their primary audience. In this case, that could be a mistaken assumption."

Matthew Graczyk: