There's no other sensation quite like it: tickling and liquid at first, so fleeting that it almost passes for imagination or wishful thinking. Then that slight tickle gives way to a gentle squirming, more solid than a flutter but still sudden and unpredictable. Then one day it's not just a twinge but a rolling, solid kick. A kick so big and real that it can be seen and felt from the outside too. Feeling your baby move in the womb is one of the best, most miraculous parts of pregnancy. Women used to call these movements quickening, and your heart does quicken, each and every time you feel the hiccupping tumble of new life inside your body.

The morning after Olivia was born I woke up - or more accurately, surfaced from beneath of fog of narcotics and anesthesia. Muddled and disoriented, I stared at the IV lines taped to my hand, the skin oddly white save for a sickly yellow wash of medicine. I had no idea what time it was, or how long I'd been unconscious. Where was my baby? Instinctively I touched my now-flat belly. As I did I felt something totally unexpected: a pang of sorrow. She's not in here anymore. The door opened, and a nurse, beaming to see me awake, strode into the room bearing my infant in her arms. The baby was tightly swaddled, with a pink knit hat perched comically on her head. The nurse eased her into my outstretched arms. It was such blissful relief to pull her close and feel her body move against mine, even if her fierce little kicks were now muffled by blankets. For months her movements had been my signal that all was well, a private language just we two shared. I didn't realize how much I'd miss that after she was born.

The new baby, or Baby X as we call her, since we've been completely unable to settle on a name yet, is a wild one. She's moved through every possible position: head up, head down, footling breach, face up - you name it, she's tried it. She's always shifting, elbowing, throwing out a foot. I've tried to savor each movement, knowing that this is my last child, and these are sensations I'll never again experience. If only it were possible to memorize a feeling, to call it up years from now and have it be as real and true as the day it happened. Though it seems impossible at the time, when you are immersed in so much novelty and drama, much of pregnancy fades into faint memory. How long before I forget just how it feels to be kicked in the ribs - from the inside?

The last weeks of this pregnancy have been filled with bittersweet realizations. The time and attention I've been able to lavish on Olivia will have to be shared now. I'm already nostalgic for the many cuddles and adventures we've had together, just us girls. Though Olivia will have a sister - something I've wished for my whole life - she also has a big adjustment to make. Is she ready at two to share her mommy and daddy? As for Eric, he's already announced that another little sister wasn't part of his master plan, especially if this one plans to poke him in the eyes and tweak his ears as much as Olivia does. He doesn't yet realize that his two sisters will grow up worshipping him, that he'll forever be their heroic big brother. Right now all he can see is a pair of tiny terrors stalking his every move and snatching at his favorite toys.

So here we are, less than 36 hours away from welcoming our new daughter into the world. We can't wait to meet her and snuggle her and discover this little person who has been sent to complete our family. Will she be cautious like her brother? Fearless like her sister? Mechanically inclined or theatrical in the extreme? Or will she surprise us by being someone we could never have imagined - and never have lived without? A baby is every possible wish and gift and surprise all at once, and it's humbling to be entrusted with the care of a new and precious soul. We have no idea what we're doing, but we're thrilled to be doing it. And maybe it's wise not to think too much. Maybe Olivia, in all her two year-old wisdom has the right idea. She's been talking to my tummy for months now. "Come out new baby!" she bellows. "Old baby wants to hold you in hands."