The Cells That Stayed

The waiting room smelled like hand cleaner and old magazines. Maya's grandmother was somewhere down the hall giving blood, and Maya and Soren had already read every poster on the wall twice.

Except one.

"This one's weird," Maya said. She stood in front of it with her arms crossed. "Read the middle part."

Soren read it out loud, quietly, the way he read things when he wanted to catch them. "During pregnancy, cells pass from the developing baby across the placenta into the mother. Some of these cells survive in her body for decades."

"Decades," Maya said.

"That's the part I read twice too."

Maya tapped the glass over the diagram. It showed a mother, and little dots leaving the baby, drifting up through her like bubbles going the wrong direction.

"Okay," she said. "So the baby's cells go into the mom. Not the other way. Into her."

"Into her," Soren agreed. He had his notebook out. His pen stopped over the page. "Where do they go, though. It just says they survive."

Maya read the next line. "Fetal cells have been found in the mother's blood, bone marrow, heart, and brain."

Neither of them said anything for a second.

"The brain," Maya said.

"That can't be a typo. It's a hospital poster."

Maya sat down in the plastic chair, then stood up again. "So a mom has a kid, and part of the kid, actual cells, ends up living inside her head. And they stay. Years later they're still there."

"Decades," Soren said, because it seemed important to keep saying it.

"How would they even know that," Maya said. It wasn't really a question to him. It was the list in her head getting longer.

Soren answered it anyway. "Boy cells, probably. If a mom has a son, his cells have a Y chromosome. She doesn't. So if you find a Y chromosome in a woman's brain, it didn't come from her. It came from a kid she carried."

Maya turned around fast. "That's how they'd prove it."

"That's how I'd prove it," Soren said. "If I were them. You find the thing that shouldn't be there and you follow it back."

"A thing that shouldn't be there," Maya repeated. She liked that. She liked it a lot.

A nurse walked past with a tray. Down the hall, someone laughed at something.

Maya was doing the thing where she chased an idea past where it was polite to chase it. "Wait. My grandmother had four kids. My mom and my three uncles."

"Okay."

"Three of them are boys."

Soren looked up from the notebook.

"So right now," Maya said slowly, "down that hall, there is a machine taking blood out of my grandmother. And in that blood there might be cells. From my uncles. From when they were babies. Forty, fifty years ago."

"And your mom," Soren said.

"And my mom." Maya's voice went a little strange. "Cells from my mom. Living in my grandmother. This whole time."

Soren wrote something. His hand moved and then stopped.

"It's not just her," he said.

"What do you mean."

He was working it out as he said it, one step, then the next. "Your mom carried you. So your cells are in your mom. Right now. That's the same thing. It has to be, it's the same door, the placenta."

Maya sat down again. This time she stayed down.

"Your cells are inside your mom," Soren said. "In her blood. Maybe her heart. And here's the part." He tapped his own poster line. "Your mom's cells are inside your grandmother. And your mom carried you and picked up your cells. So some of your cells and your mom's cells and maybe even a little of you is riding around in your grandmother too. You go back a generation you weren't even there for."

"Stop," Maya said, but she was grinning, the grin she got when something was too big to fit and she loved that it didn't fit.

"You stop. You started it."

"Do the other direction," she said.

"What other direction."

Maya leaned forward. "My grandmother has cells from four kids in her. But her mom had cells from her. So my great-grandmother, who I never met, might still have been carrying my grandmother's cells when my grandmother was a baby. And on and on backward."

"And forward," Soren said. "If you have kids someday you'll carry their cells. Plus you're already carrying whatever your mom left in you."

Maya stared at the diagram with the little dots going up the wrong way.

"So nobody's just one person," she said. Not dramatic. Just checking if it was true.

Soren didn't answer that. He read the last line of the poster instead, the one they'd both skipped. "Scientists still don't fully understand what these cells do once they're there. Some may help repair the mother's tissues. Their full role is still being studied."

"They don't know," Maya said.

"They don't know." Soren closed the notebook halfway, then opened it again. "Cells from a kid, sitting in a mom's heart for forty years, and nobody knows if they're doing anything, or fixing something, or just there."

"Just there," Maya said quietly. "Like they're keeping her company."

"You can't put that. That's not science."

"I know. I'm not putting it anywhere. I'm just saying it."

Down the hall, a door opened. Maya's grandmother came out slowly, a bright bandage in the crook of her arm, pressing it with two fingers the way you're told to.

Maya didn't get up right away.

"What," her grandmother said, seeing her face. "Do I have something on me."

Maya looked at her grandmother's arm, at the bandage, at the small dot of red starting to show through the white.

"Yeah," Maya said. "Sort of. A lot of people, actually."

Her grandmother laughed, not understanding, and held out her free hand. Maya took it and looked at the back of it, at the blue lines under the skin, at the blood moving through with everyone in it.