Even though I knew, intellectually, that a lot of the 40+ pounds I gained during pregnancy was fat reserves for nursing, increased blood volume, amniotic fluid, a brand new organ, and so forth; when my son came out weighing just seven and a half pounds, part of me spent the next few days thinking, “But where is the rest of you, really? Do you have a secret twin hidden somewhere?” One of the many things you learn about your body after pregnancy, is just how many big changes a tiny person can make.
It's certainly possible to know and understand that bodies are amazing before having a baby, or without having one at all. But few things, if anything, can give you an in-your-face, visceral understanding of just how amazing, bewildering, funny, and raw your body, is like having a baby. Tiny cells, invisible to the naked eye, transform into a whole new person inside of you, and put your body through all sorts of changes in the process. Then you spend hours, or even days, moving that person out of your body; a feat that requires levels of strength and energy most of us never imagined we had. Then we actually have to keep that new person alive, which in the earliest days is an incredibly energy-intensive task.
Before I had kids, I truly didn't understand just how hard it is to have and raise a baby, or how quickly you rise to that previously impossible-seeming task. I mean, I thought I did, but it didn't take very long for me to realize that I simply didn't have a clue. I learned, though, as well as a whole lot of other weird, surprising, and impressive things about my body, including: