Radiolab - Everybody’s Got One

Episode Date: August 20, 2021

We all think we know the story of pregnancy. Sperm meets egg, followed by nine months of nurturing, nesting, and quiet incubation. But 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 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. This episode was reported by Heather Radke and Becca Bressler, and produced by Becca Bressler and Pat Walters, with help from Matt Kielty and Maria Paz Gutierrez. Additional reporting by Molly Webster. Special thanks to Diana Bianchi, Julia Katz, Sam Behjati, Celia Bardwell-Jones, Mathilde Cohen, Hannah Ingraham, Pip Lipkin, and Molly Fassler.   Support Radiolab by becoming a member today at Radiolab.org/donate.     For cool new research on the placenta: Check out Harvey’s latest paper published with Julia Katz. Sam Behjati's latest paper on the placenta as a "genetic dumping ground". 

Wait, you're listening to radio lab from WNYC. Oh my god. Oh my god. Hey, I'm Lulu Miller and I'm Molly Webster. This is Radio Lab. It's like Red Velvet Bread. Look at that. It does look like a loaf of bread.

And today on the show, a round loaf of homemade bread. With veins that's purple and red. We have a story about a thing. But also like blood sausage bread. I think 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 Pressler. Well, I think I think I can

I take it. Okay. Um. I was thinking about getting pregnant, and I started to do a bunch of research. And pregnancy is this thing, at least for me, where I was like, I know about that. 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. 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. Bap, bap, bap, let me turn it down. Your whole life, you've got your heart, your lungs, your bone, your skin, your eyes, et cetera. 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. I had heard of the placenta before, but I really didn't know anything about it. It's called the afterbirth for a reason. It's an afterthought that no one thinks about. I think I thought a thing a lot of people think, which is that the baby grows inside the placenta. I definitely thought balloon baby was inside of.

I mean, okay, I was pregnant and I think I thought it was just like extra lining on my uterus, but it's not. It's not even yours. The placenta belongs to the embryo, to the fetus, to the baby. Huh. 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 Climax. 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.

Kristen, I think we need another cabinet. But before we do. I'm interested in how you got interested in the plethora. Presumably it wasn't because you got pregnant. Serendipity. So about 40 years ago, Harvey's just gotten out of medical school. And I'm now a resident at University of Pennsylvania. And I'm in a laboratory studying ovaries. And in the lab, there was somebody else who was working on the placenta. And they were chopping up the placenta

and homogenizing the placenta. And these other scientists in the lab ended up with this thing called a gradient where the different kinds of cells in the placenta were sort of separated out. They can look at them independently. And they wanted me to take a picture of the gradient. Why?

Well, on the side, I'm a photographer. I've actually done bar mitzvahs and weddings. Oh my gosh. Things like that. Yeah, I love, I'm visual things. I think is what interests me in general. And so I took a picture of the gradient and I asked Jerry, who is running the lab. So Jerry, would you mind if I looked at what they are?

He said, sure, go for it. And what Harvey saw was something that no one had ever seen before. He saw these cells, sort of a bubbling cauldron of cells. They were like a meba. 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 multi-nucleated 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 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. Edgy came in on this organ I have had and know nothing about. Alright, 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. So, let's start from the beginning. You have an egg and then if they're sperm around, the sperm will fertilize that egg and then it divides. It divides into two and then four, eight, and 16, etc, etc. By the time it gets to about 32, the cluster of cells sort of forms into two layers. It's like a tennis ball now. There's a little cluster of

cells on the inside. That will become the embryo. That will become the fetus. That will become the baby., that will become the fetus, that will become the baby, those little inside group of cells. But the cells on the outside. Those cells will become the placenta. So from the very first few days of pregnancy, these placental cells are wrapped around what's going to become the embryo, like a little blanket. And as Harvey explained all this to us, and he walked us deeper into the story of the placenta, we started to see that pregnancy isn't a peaceful nursery rhyme kind of a story

about a pregnant person nurturing a fetus until it becomes a cute little baby. It's actually more like a struggle. And not like a calm college debate. It's like a cage match, like a knockdown drag out boxing match or a tiny war maybe even. On one side is the pregnant person, on other side, is the fetus. And in the middle, or maybe not, like, actually, in the middle, more like, actually, like, in the corner rubbing the shoulders of the fetus

is the placenta. So what happens? Well, okay, so Harvey says the first thing you have to understand is that that tiny embryo with its little baby placenta cells wrapped around it like a blanket. It is not welcome in the mother's body. From the mother's point of view, this is immunologically foreign. You know, the pregnancy is a little bit genetically the mom, but also a little bit the dad, 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... What is it? Some kind of... Cloak. Before the mother's body even has a chance to attack the embryo, the placenta blanket hides it.

The placenta is going to become invisible to the mother. What? Yeah. The mother literally doesn't even see that the pregnancy is there. Mom's still at the bar. She's serious. OK, so for the first week or so of the pregnancy, the placenta is pretty much just hiding the embryo

from the mother. But then? The next problem that the placenta faces is nutrition. The embryo gets hungry, and the placenta is like, I gotta feed this thing. And this is when the battle lines really start to get drawn, because essentially this war between the placenta and the pregnant person is a war that's about food. The placenta harvies says has one mission. To make the biggest baby possible to suck as much nutrients out of the mother as possible.

And the pregnant person's mission? Not to die. So the placenta is in the uterus, looking around for food. And it does this thing, something kind of tricky. Something that, when we heard about it, actually feels like it's skipping ahead nine months. Harvey says it produces this hormone.

HCG. Happens to be the hormone that activates pregnancy tests. But one of its other jobs is that it... It causes the lining of the uterus to secret a protein. That our friend Harvey likens to milk. Wait. What?

Like no. The vitality you get from milk lasts far longer than energy from other drinks. The lining of the uterus makes milk for the embryo. I'm to get back to the refill. That is wild. Yeah. for the embryo. I'm to get back to the refill. 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 placentaate forms tendrils like long skinny claws. It actually tried to invade in up through the uterus into the maternal body. Into the blood vessels and attack the walls to open them up. Like, I'm gonna suck all your nutrients from you. But...

Uh-uh. 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. It keeps digging. But then the uterus blocks it. And what you start to see is this push and pull,

where the placenta keeps digging, digging, digging. We're talking pretty aggressive here. And the uterus keeps blocking it. Blocking, blocking it. Wait, digging, digging. We're talking pretty aggressive here. And the uterus keeps blocking it. Blocking, blocking it. Wait, wait, wait. Can I just ask, like, why isn't this, like, isn't our whole point to carry on? Like, isn't that what evolution has built us to do?

Why would this moment where it's about to happen be so combative? It's a really good question. And we will get to it after the break. This is Marnie Campbell from the beautiful banks of Lake Washington and Seattle, Washington. Radio Lab is supported in part by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.Sloan.org Science reporting on Radio Lab is supported in part by Science Sandbox, a

Simon's Foundation initiative dedicated to engaging everyone with the process of science. Lulu, Molly, Heather, Becca, Radio Lab. Today, we are telling the story of the placenta, a story which has revealed to us just how much pregnancy itself is like a war between the fetus and the parent's body and what we were just getting around to was why. Right. So you all actually already answered this question on the show. Oh. Rob, this came to total shock to me because after all the thing.

So basically the story we told then is that before placentas, all animals that would become mammals, late eggs. And an egg is a special little thing. It's a self-contained little package where the fetus has everything it needs to eat until it's ready to hatch and all of its waste products stay inside the egg and nothing comes in and nothing goes out until the animal is ready to leave its egg. But then a virus infected an ancient proto mammal and changed its DNA so that eventually many generations later, the egg shell transformed from a hard shell that exists outside the

body to a sort of permeable layer that exists inside the body, which then becomes the placenta. And this was a huge advantage because it made it possible for the blood of the mother to actually feed the fetus. So it could get tons more nutrients. It wasn't limited to just like whatever yolk was inside the egg from the beginning. And the individual was so reproductively successful that it spread across all euetherian mammals.

Geneticist Melissa Wilson again. That's mind blowing. Because it made it possible to actually make a baby with a big giant brain, like a human being or a dolphin. And that was great. But it also had this downside. This wonky interaction between the pregnant individual and the placenta, because the placenta

is not the DNA of the pregnant individual and the placenta, because the placenta is not the DNA of the pregnant individual. The placenta is the DNA of the offspring. Okay, and this is how we've ended up four weeks into what's basically a war between the mother and the placenta, with the placenta trying to suck blood out of the mother, and the mother basically trying to box it out. And this fight is just getting started.

Week 5 goes by, then week 6, week 7, the embryos growing eyes, ears, bones. It has a hard kidney sliver. Meanwhile, the placenta is digging, digging, digging, trying to get to the blood to get this thing more nutrients. But the placenta just can't break through. It's just like, Hey, I need to be growing. I need more nutrients for my passenger, the fetus. And the uterus just says, Nope.

Get out. But the placenta has a couple tricks up its sleeve. Specifically one trick called Pp13. It's a protein that Harvey says creates a diversion. Here's an analogy. If we wanted to rob a bank, I don't want the police to be near there. So what I'm going to do is blow up a grocery store, wait for all the police to sort of go

around the grocery store, and while they're busy doing that, I'm going to sneak into the bank. So in the world of Harvey's uh, analogy here, PP-13 is blowing up the grocery store. The placenta produces it. It goes off to some other part of the uterus that the placenta isn't trying to invade. And there...

The PP-13 attracts the entire police force SWAT team, everybody of the mother's immune system. And while the whole police force is over there everybody of the mother's immune system. And while the whole police force is over there dealing with the PP-13, the placenta's digging claws bust... ...strip. And... Blood fountains into the placenta.

It's bathed in all these nutrients and goes by fay time. Let me see what I need. As the mother's blood starts rushing into placenta, the fetus just starts growing and growing. It's the size of a grapefruit by week 15, a pineapple by 24, a watermelon by 36. That fetus is demanding more and more horsepower, more and more nutrients to actually grow. So the placenta starts releasing more and more of this hormone, called human placenta lactogen, which sort of hijacks the mother's digestive system. It says, okay, you're eating, I get that.

But none of that actually is for you. You're not going to get to store it. All those nutrients are going to stay in your blood. So I, the placenta, can suck up those nutrients. And all the while, the placenta is gobbling up more and more of the mother's blood. And by the third trimester, Harvey says, 20 to 25% of all the blood flow of the mother is going into the placenta. And this is where things can get dangerous for the mother.

If the placenta and the fetus together say, hey, I'm not getting enough blood, I'm just gonna force her body to start pumping more blood into me into the fountaining system. And this is a condition we call preeclampsia. Preeclampsia is very, very scary. And it's basically when the mother's blood pressure spikes so high that she can actually die. Well, and it's really serious.

It's one of the leading causes of maternal death. And I think it's easy to sort of think like, blood, high blood pressure, you know, not such a big deal, but it's actually the placenta, you know, sucking so much blood out of the mother's body that she can't continue to survive. And this can also go wrong in the other direction. Mom, of course, doesn't continue to survive. And this can also go wrong in the other direction. Mom of course doesn't want to die.

She doesn't want the fetus to take all of her nutrients, but if she is successful and wins the battle, if you will, the placenta is too small, the fetus is too small, and the pregnancy may not survive. But, if neither side wins the war, then after nine months, give or take a few weeks. Poof! You have a baby. And Poof is exactly what it feels like. But the placenta is still in there. And so the placenta actually also kind of has to be born.

I'm getting the sense that the placenta may be underneath this blue cover. Is that right? Good guess. So we didn't actually see anyone give birth to a placenta. But Harvey did show us what in his lab. Alright, are we ready for the moment? Harvey grabs the blue cloth and he pulls it back. And this is the placenta which is in the standard ziploc bag.

That's what it's in right now. Oh my god, I mean it looks so, it looks very organic. It's kind of bloody isn't it? It's so bloody. And so I'm going to open the ziplock bag It's so bag like it's a bit bluer than I thought It also kind of looks like rom meat like you would make a hamburger or something. It is rom meat So I'm gonna pick it up and see how heavy it is. So I grabbed the placenta. It's like a hamburger or something. It is raw meat. So I'm gonna pick it up and see how heavy it is.

So I grabbed the placenta. It's kinda heavy. Like what, like a normal term placenta is about 550 grams, which is just about a pound. It's about eight to nine inches in diameter. About as wide as a volleyball. It's really weird. It's okay, first of all it's cold.

Maybe slimy is the word, and it's got a lot of texture when you're in the beefy part. You can feel what I imagine are the veins, and it has like, it's not all one texture. It's like hard in spots and soft in spots. It feels sort of like crazy. And then Harvey told us how the placenta, this little alien invader and all its thirsty veins and tendrils and hooks, how it leaves the body. I think this is another miracle.

So the baby goes first and... The uterus is elastic and has muscle, so it contracts down. And it's that contracting down that actually shears the placenta off, is elastic and has muscle, so it contracts down. And it's that contracting down that actually shears the placenta off, the lining of the uterus, and the placenta gets delivered. And then... All those blood vessels that have been supplying blood to the placenta for all those

weeks and months have to close down. And they do. Like immediately, there's this river of blood fountaining into the placenta that just shuts off. And what's kind of cool is that it leaves no scar. It's like one of the only things like this in the body, maybe the only thing like this, where something sort of gets sheared off and there's no like no mark remains. Oh, that just makes me think that while from the outside it feels like such a push and pull

and like they're competing against each other that like in the scarlessness there is like a comradery and a piece of sorts. Yeah, in some sense, I think of it as like the OG parent for the baby. It's one mission is to help that embryo grow into a healthy fetus and deliver a baby. And it's developed this sort of like incredible way of somehow making sure all of its needs are met

in such a selfless way that I've started seeing it as the first parent. Yeah, I don't know. I feel like I'm going to cry. It feels like, here's this thing. This is somebody's baby's life thing. I don't know. But so, okay, placenta comes out. It releases. It leaves no trace. it leaves no scar. It knows it's time to let those grappling hooks go, comes out. And then what's the end of the journey? I mean, I guess it goes in the garbage most of the time. I feel really sad that I can't meet mine. I think once you know all that it's done for you,

I just wish I could meet it. I think once you know all that it's done for you, I just wish I could meet it. And thank it? Yeah, and hold it. Was that for making me survive and be alive? Put it in my closet, I don't know. But also a lot of people don't throw it away. Only recently are we beginning to see that scientific discourse is taking the placenta seriously. This is Tina Delisle.

She's a professor of history at the University of Minnesota Twin Cities, and she's writing a book about the placenta. Indigenous people were understanding the placenta for a long time. She explained to us that this dawning we were having that the placenta is kind of like a parent. It's something that a lot of people had already been thinking about the placenta for a really long time. In native cultures, the placenta is a friend, a companion grandmother. And when you think about the placenta that way, as a relation, they're going to treat it very differently, and that explains why. Throughout a lot of native cultures, the emphasis is on proper burial of the placenta. Tina explained

that you see this practice of bearing the placenta all over the world. In various African cultures, in Native American culture, in Hawaii, French Polynesia, in Altearoa, Tahiti, Vanuatu, and where she's from. Born and raised in Guahan in the Mariana's. For Chamorros, the indigenous people of Guam, when you bury the placenta or the gatsum, it ensures that baby's safety. You know, even examples like when they're young and they're learning how to walk, it protects them so they don't fall down. It was a way of protecting children into adulthood. Huh. Okay. So you're saying that the placenta isn't just looking after

the well-being of the child when it's in the womb, but also into adulthood? Yeah, but also for the well-being of the land. Because when you plant the placenta, it connects people to place. The idea is that if someone moves away, they always remember my placenta is buried there, and they will take care of that land. Did you bury your kids placentas? No. I had inquired about

the possibility of taking home the placenta. This was 2006, Tina was living in Michigan. When I was there, I was told that, and when I say there, this is when, you know, in the middle of labor, and I was told that they wouldn't let me take home my baby's placenta. And why is that? Like, why wouldn't they like it? Because of the law. And I was told that I'd have to go to court to get that.

It would be really difficult. How did that make you feel when you heard that? You know, I felt really bad about that. I had my partner. My husband take pictures and video of the placenta, right? And he's like, okay. I need something to remember. My baby's placenta was right.

But things have changed some since Tina gave birth in 2006. In states like Hawaii and Texas and Oregon, now you can legally take your baby's placenta home with you. The only consolation I had really was maybe this will be different next time around for my daughters. I'm just going to give you a big step back. And this is the Santa of Silvergates today? Monday, actually. Monday, late afternoon. Yes, so there's a little cute baby someplace who is happy and alive because of this placenta.

Yes, we got to send that family this podcast. I'm sure we can't know who they are hip-bub. We can't. We know who they are. That's part of the reason we have the placenta. But let's thank them anyway. Thank you. More spiritual. Yes, we will thank them spiritual. This episode was reported by Heather Radke and Becca Bressler, and produced by Becca Bressler and Pat Walters with help from Matt Kilti and Maria Paz Gutierrez. Special thanks to Diana Bianchi, Julia Katz, Sam Bajadi, Celia Bardwell Jones, and Hannah Ingramham. Special thanks also to my placenta, forgetting me here, thanks to the placenta of all the

people who made this program. Thanks for building such talented humans, and finally to the placenta that made you, listener. Thanks for making such a dorky human who likes our program. Really appreciate it. Alright, that'll do it by. You want half of the cookie? Yeah! You have to do it, mommy says.

Then you gotta repeat what I say, okay? Right. Radio lab was created by Radio lab. created by real love reclated by drop emm rod and by so clear blue Miller was a snuffler our hard course course in the

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