Any new parent or parent-to-be eagerly anticipates their child's firsts: first smile, first tooth, first steps. These are the quintessential milestones & memories of a child's early years. There are spaces in baby books to record the dates, circumstances, and photographic evidence of these momentous occasions. I've noticed, unfortunately, that the idea of potentially missing these important events... specifically by a working mother using childcare...has also been used as ammunition in the "mommy wars" and feeds into a lot of working-mom guilt. I see a lot of "Oh, I couldn't go to work and leave my baby! What if I missed her first steps?!" I admit, those thoughts worried me during my first pregnancy. How horrible would it be to miss the very first step/word/jump/etc...?
Of course, what you realize soon enough, is that the "firsts" are not a one-time-only, line-in-the-sand transition. Your baby does not go from grimly not-smiling to suddenly smiling. Its fuzzy. It comes in fits & spurts, and it may take you a while to catch on to what your baby is doing. "Was that a smile" Or gas? Probably gas"...and then the next day "No, that must have been a smile? Nope he's pooping"...and finally 2 days later "OH, that IS a smile...maybe those other ones were, too?" Its the same with walking, and talking. Even in the midst of it, I wasn't sure what B's first word was. Was it the "goggy" he kept saying, that I thought was babbling, but later learned meant "doggy"? Or the loud and clear "BUS!" he yelled on the street one day? Did the "da da" count as "daddy?" or the "bobby" as "mommy"? For the most part, childhood is a continuous progressive development and not markers on a time line or lines in a baby book. Unless you literally do not see your child for days at a time, there is no way you are going to miss the "saying the first words" transition or the "learning to walk" transition.
The other point is, of course, even if you stay at home full time, unless you are constantly with & have your eyes on your baby you may indeed miss parts of their life. L started rolling over recently. G saw him do it last weekend, while I was showering. That evening, I spent 30 minutes playing with L on his playmat, trying to coax him to roll over again. No dice. Then I went to go get B some milk, and when I came back, he was on his tummy! I haven't seen it yet, but when I do, it'll be just as exciting to me because its new TO ME.
And that's the bottom line. Maybe your child does take his first tottering steps at the daycare, or sing his first song during circle time. Until you really see it, its hard to believe that he's actually doing it. When he does it in front of you, it'll be amazing for you. And when you exclaim and grab the camera, and hug him tight...it'll be amazing for him, too.