This is what I have learned from my association with a large group of Mommy Bloggers over the past year and from being the CMO of e.l.f. Cosmetics.
Moms pride themselves on being savvy consumers who can sniff out a poseur brand. Brands need to be the conduit for information to moms from other moms and from experts, but be wary of star power... celebrities don’t cut it. Marketers that have a mom’s trust have worked to earn it, by making good products, offering relevant advice and engaging those moms. All peers have influence to some degree... especially when marketing to women so the more you understand the relate to the community the better off the brand. If you market to women recognize and benefit from the value women place on authenticity. Women are busy with multiple responsibilities so keep your site's navigation intuitive and simple, and keep your message clear and concise.
The bottom line: Brand marketing (especially to women) in a social media world... it's about relevance, transparency and authenticity.