We all think we know the story of pregnancy. Sperm meets egg, followed by nine months of nurturing, nesting, and quiet incubation. this story isn’t the nursery rhyme we think it is. In a way, it’s a struggle, almost like a tiny war. And right on the front lines of that battle is another major player on the stage of pregnancy that not a single person on the planet would be here without. An entirely new organ: the placenta.In this episode, which we originally released in 2021, we take you on a journey through the 270-day life of this weird, squishy, gelatinous orb, and discover that it is so much more than an organ. It’s a foreign invader. A piece of meat. A friend and parent. And it’s perhaps the most essential piece in the survival of our kind.Special thanks to Diana Bianchi, Julia Katz, Sam Behjati, Celia Bardwell-Jones, Mathilde Cohen, Hannah Ingraham, Pip Lipkin, and Molly Fassler.EPISODE CREDITS: Reported by - Heather Radke and Becca Bresslerwith help from - Molly WebsterProduced by - Becca Bresslerwith help from - Pat Walters, Maria Paz GutierrezEPISODE CITATIONS:Articles:Check out Harvey’s latest paper published with Julia Katz.Sam Behjati's latest paper on the placenta as a "genetic dumping ground". Signup for our newsletter!! It includes short essays, recommendations, and details about other ways to interact with the show. Sign up (https://radiolab.org/newsletter)!Radiolab is supported by listeners like you. Support Radiolab by becoming a member of The Lab (https://members.radiolab.org/) today.Follow our show on Instagram, Twitter and Facebook @radiolab, and share your thoughts with us by emailing radiolab@wnyc.org.Leadership support for Radiolab’s science programming is provided by the Gordon and Betty Moore Foundation, Science Sandbox, a Simons Foundation Initiative, and the John Templeton Foundation. Foundational support for Radiolab was provided by the Alfred P. Sloan Foundation.
Chapter 1: What is the concept behind the podcast episode 'Everybody's Got One'?
All right.
You're listening to Radiolab.
Radiolab. From WNYC. WNYC.
Oh, my God. Oh, my God.
It's really similar. Hey, I'm Lulu Miller. And I'm Molly Webster. This is Radiolab. And today... It's like red velvet bread. Look at that.
It does look like a loaf of bread.
We are dredging up an episode from the archives. It's called Everybody's Got One. And I really love this story so very much. I hope you enjoy. A round loaf of homemade bread.
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Chapter 2: How does the placenta play a role in pregnancy?
With veins. That's purple and red. We have a story about a thing. But also like blood sausage bread. A thing that we've all had at some point. It is patty like. But most of us, we never even knew it.
And it comes to us from our contributing editor, Heather Radke. Yeah, I'm not even on staff. And I wish you were, producer Becca Bressler.
Well, I think I can... You take it. Okay. I was thinking about getting pregnant, and I started to do a bunch of research about And, you know, pregnancy is this thing, at least for me, where I was like, I know about that. You know, I took like 14 years of sex ed in my public high school.
But I'll just say the more I learn about it, the more I realize how little I know and maybe like how little anyone knows about pregnancy. Yeah. And one of the very first things I discovered was that when you're pregnant, you don't just grow a baby. You grow an entirely new organ.
Let me turn it down.
Your whole life, you've got your heart, your lungs, your bone, your skin, your eyes, etc. So this is the main hospital. But then all of a sudden during pregnancy...
A whole new organ shows up. Here is our cabinet of placentas.
And that organ is the placenta.
Whole placentas, pieces of placentas.
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Chapter 3: What discoveries did Harvey Kleiman make about the placenta?
So it's actually grown by the fetus, which means that every single one of us has had a placenta.
I was kind of like you. I literally had no idea what it did, what its purpose was.
This is Harvey.
Harvey Kleiman.
He studies the placenta.
MD, PhD, physician scientist at Yale University.
Where he has a cabinet of placentas.
We're sort of running out of room.
Which we visited. We'll come back to that.
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Chapter 4: Why is pregnancy described as a tiny war?
They were like amoeba.
Later, he'd make movies of them.
They started moving around and then they came together, they aggregated, then the membranes broke down and they fused to make these multinucleated giant cells.
They were growing very aggressively in a way that surprised him.
I said, that is super cool. What's going on here?
Eventually he figured out that what he was looking at were stem cells, placental stem cells. And over the next few decades, he and a bunch of other scientists would start to piece together the story of the placenta.
And that's the story we're going to tell you.
Cool. Okay. I'm so excited. Educate me on this organ I have had and know nothing about. All right.
So before we start, we just want to say a note on the word mother. Not everyone who gets pregnant or has a baby identifies as a mother, but it's a word a lot of people use when talking about pregnancy, including some of our sources. And so we're using it in addition to more inclusive language like pregnant person and parent. Got it.
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Chapter 5: How does the placenta interact with the mother's body?
Exactly.
Which, for the mother's body, is not normal.
If we took a piece of tissue from whoever the father was of a pregnancy and put it into the mother, she would reject it.
Right, because not-self shouldn't be there. Not-self is a virus. Not-self is a bacteria.
Melissa Wilson, geneticist at Arizona State. We need to get rid of not-self.
It's a foreign invader.
And so if an embryo just waltzes into a uterus one day without a little placenta blanket around it, the mother's body would gather up a squad of white blood cells, send them out to find it, shred it apart, and kill it.
So that's definitely a problem.
But... Before the mother's body even has a chance to attack the embryo, the placenta blanket hides it.
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Chapter 6: What mechanisms does the placenta use to gain nutrients?
The lining of the uterus makes milk for the embryo.
Time to get back to the refills. That is wild.
Yeah. But this milk is like a snack for the placenta. What it really needs is blood. So at this point, about two weeks into the pregnancy, the placenta goes on the offensive. By now, it's actually latched onto the side of the uterus.
And at this point... The placenta forms tendrils. Like long, skinny claws. That actually try to invade in up through the uterus into the maternal body.
Into the blood vessels and attack the walls to open them up.
Like, eh, I'm gonna suck all your nutrients from you. But...
The uterus stops them. Basically putting up a brick wall, very dense tissue.
To block those claws from getting in.
Now the placenta doesn't give up easily.
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