When I first learned that my son was swimming around in my belly I craved nothing more than information.

I wanted to know how big he was and how fast he was growing and when he would get his arms and his fingers and his eyes. I wanted to know when my belly would begin to swell and when I would begin to really feel pregnant.

I dug into my grad school books on fetal development and signed up for weekly emails on my baby’s growth but, still, the information was vague, all averages and anecdotes. I didn’t care to know that the average woman began to show between 12 and 20 weeks, or that her labor often lasted between 16 and 24 hours or that the average baby was between 7 and 7.5 lbs. I wanted to know when I would start to show and how long my labor would be and how much my little one would weigh.

To satiate my curiosity for personalized information I turned to the woman whose experience I thought mine would most closely mirror – my mother.

As we laid together on the couch, talking about the future, I asked her about the past. I wanted to know what time I was born: “Sometime in the morning,” she responded. I asked how much I’d weighed and how long I’d been: “A little under eight pounds and pretty long but not that long,” she said.

I was shocked that the details of my early life had been somehow lost over the decades.

Confused by the vagueness of her memory I dug deeper.  My first food? She didn’t remember. My first word? She thought it was “car” or “dada,” but it was tough to recall. She didn’t remember exactly how old I was when I first rolled or crawled or walked, though she guessed for each. I understood it had been a quarter of a decade since the events I was asking her to recall had taken place, but I was shocked that the details of my early life had been somehow lost over the decades.

When I asked what she did remember, she told me about how happy I was on the day I met my little brother and the way I used to stay up late talking to my sister who wanted nothing more than to go to sleep. She told me about swim lessons and softball games and afternoons barefoot in the creek. She also talked about middle school dances and high school tears and the fact that even now, pregnant with my own child, she still saw me as her baby.

As my belly grew, question after question that had raced through my mind in the early weeks of pregnancy was answered. As it turned out, I would never have morning sickness, I would start to show around 14 weeks and I would gain over 40 pounds. My pregnancy would last exactly 40 weeks, contractions started just after 4 a.m. on his due date.

On the day of my son’s birth, more answers fell into place: Labor was nine hours, he drew his first breath at 1:19 p.m. He weighed 9 pounds, 9 ounces and was 21 inches long. His eyes were slate blue, his head nearly bald. His knees were thick and his cry, soft and sweet, left me breathless with joy and disbelief. It was the most wonderful day of my life and I swore, in the moment, that I would memorize every detail, and hold onto the memories forever.

As I began to test my memory I realized that there was already so much I had forgotten.

A few weeks ago, just after my son’s second birthday, I was chatting with a friend about my boy and how quickly he’s grown. I recounted the day of his birth, still beaming with pride and overcome with joy. “Was it cold on the day he was born?” she asked, and suddenly, I couldn’t remember.

I’m sure it was, he was born in January, but I couldn’t remember a thing about the weather on the day of his birth. As I began to test my memory I realized that there was already so much I had forgotten: What I had done the day before his birth, what I packed in my hospital bag, what my boy wore home from the hospital, and how we spent his first afternoon once we got there.

Though the prospect of losing these details once puzzled and horrified me, in that moment, I began to understand. Once, my boy was just an ultrasound. I treasured the curve of his elbow and read tenderness into the way he sucked his thumb in the grainy black and white image. I swore I wouldn’t forget when I’d felt the first kick.

And then he was a birth story, the hours and the pushes and the weight and length, and I treasured the details of his arrival, ascribing kindness to his promptness. I swore I would remember them all. And then he was a first roll and a first babble and a first laugh. I treasured them all, trying my best to capture them in video or journal or photograph. Now he’s my boy, strong and tender and kind, and as I treasure every moment of his early boyhood, I’m trading old memories for new ones.

The human brain can only hold so much.

The human brain can only hold so much. The memory of the weather on the day of his birth was probably replaced with the memory of his first steps, with the way his hand slowly loosened its grip as his foot stepped forward. The memory of the contents of my hospital bag was likely replaced with the memory of his first day of preschool and the nerves and tears that swallowed us both.

The memory of his first outfit and what we did when we got home from the hospital was probably replaced with the memory of his first joke, told just last week. My boy, becoming skilled in avoiding bedtime, called me into his room with a panicked sounding, “Mommy! Hanky foot stuck!” I ran in to help and, when I noticed his foot was neither tangled nor trapped, I asked, “Stuck where buddy?” With a giggle and a grin he spit, “To the end of Hanky’s leg!”

If these are the memories that stick or, if someday they disappear too, replaced by something even better, I think I’ll be okay with that.