If there was ever a market segment that gets attention in big chunks (whether deserved or not) it’s the moms of the world. There are mommy bloggers who have held sway over brands and made brands bend to their will at times. The Motrin incident (sounds like social media’s answer to The Bourne Ultimatum doesn’t it?) was evidence of how this group can make a fuss and create change. This powerful market segment demands the attention of the online marketer in many areas because it is estimated that moms control 80% of household spending annually which represents a whopping $1.7 trillion (with a T).

eMarketer and BabyCenter is providing some insight into how this group works and the changes that occur in online behavior when a woman turns into a mom.

“Moms want to do business with retailers that are respectful and responsive to their needs and concerns,” said Jeffrey Grau, eMarketer senior analyst and author of the new report, “How Moms and Retailers Interact Online.”

About 85% of online moms said having a baby changed their purchasing habits, according to “21st Century Mom,” a 2009 study published by BabyCenter, an online community for expectant and new moms. The report also found widespread changes in media usage among moms—many of whom used both mom-centric and mainstream social media sites more than before.

Here how those habit are impacted by the addition of a little one.

The obvious change is the shift to mom-centric social media outlets but even more startling is the near disregard for traditional media. So if you are responsible for marketing a product to this particularly influential group of online buyers you better be on your guard. It doesn’t take much to set off a firestorm amongst this group if they feel that you, the marketer, has not been respectful or responsive to their needs.

Since these ladies are used to handing out discipline it might be good policy to pay attention and fly straight. Just ask Motrin.