I want to agree with this article on Slate by Nicholas Day bemoaning the milestone mania parents might experience as their children learn to do things like roll over, sit up and speak. Just the other day I was filling out a Kindergarten form for my daughter and it asked when she first did all sorts of things. I was annoyed, and I didn't remember any of it except for walking because both my kids walked "early," around ten or eleven months and because they were (and still are) on the short side, a lot of parents were a little freaked out by my walking babies.
And yet, and yet....when my son was two-and-a-half, he couldn't jump with two feet off the ground simultaneously. I asked my pediatrician about this. He said, "Don't worry. If he can't jump with two feet off the ground but can pedal a tricycle, he's fine." A few months later, Elliot would ride tricycles, but by pushing them with his feet, not pedaling. When he didn't hit a developmental milestone it was, in fact, meaningful, a tip off to some of the sensory issues he lived with and the kind of help he'd need.
Towards the end of the Slate article, Day writes: "Rather than a multitude of milestones, parents would sleep better with fewer but more relevant guidelines, an acknowledgement of how unstructured infancy actually is."
This makes sense, of course. (The bigger question I'd have might be not what parents do when their kids reach milestone (clap!) but what they do when they don't.)
We could all stand to take a deep breath on all kinds of things when it comes to our kids. Whether or not my kids "made" milestones never kept me up at night, my actual babies did that. But sometimes, you've got to be attentive because sometimes, they matter.