Sometimes, it's hard to tell the sex of a (clothed) baby. Hair has not fully grown in yet, clothes can be deceiving, and there is really no "voice" to speak of yet. So, I generally make it a practice never to use a masculine or feminine pronoun about a baby unless I have definitive evidence about their sex. (For example, at a circumcision, it's easy. When there's a big pink bow, it's pretty easy too. At the hospital with "it's a boy balloons"...pretty simple call).
So don't call Bud my son, you jackhole at the grocery store. She's wearing an f-ing pink shirt, and just because the stroller is light blue, isn't it safer to go with the clothes? And, if you are unsure, isn't it safer not to say anything at all? I would assume that offending a parent by acting as if you can't tell the sex is better than offending the parent for getting it wrong.
(And speaking of foot-in-mouth disease....I do realize that in a previous post, I suggested that the Yanks should divest A-Rod. So, I stand corrected...he's off to a great start this season (and in today's game vs. the O's).)