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My Keurig brewer from Walmart always comes in super clutch. I got it so I can keep grinding on my paper. You know I'm hitting that deadline. I also got it so I can stay up late to do some exam cramming. And of course, you know I'll be ready to stroll into my morning class sipping in style. I guess you could say it's a literal lifesaver. Cheers to that. Shop your coffee fuel needs at Walmart. Listener supported. WNYC Studios. Wait, you're listening? Okay.
All right. Okay. All right. You're listening to Radiolab. Radiolab. From WNYC. Oh, my God. Oh, my God. It's really similar. Hey, I'm Lulu Miller. And I'm Molly Webster. This is Radiolab. 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. 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. 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. 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. Yeah.
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. 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...
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 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. Kristen, I think we need another cabinet. But before we do... I'm interested in how you got interested in the placenta. 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 and things like that. Yeah, I love visual things, I think is what interests me in general.
And so I took a picture of the gradient and I asked Jerry, who was running the lab, I said, "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 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.
- So let's start from the beginning. You have an egg, and then if there's sperm around, the sperm will fertilize that egg.
And then it divides. Divides into two. And then four. Eight. And 16, et cetera, et cetera. 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. 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 and on the 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.
So what happens? Well...
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. Exactly. Which, for the mother's body...
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. 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... My body!
The placenta blanket hides it. That's an invisibility cloak. I'm invisible. 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 sure is. Okay, 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's 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, Harvey 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, 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... Causes the lining of the uterus to secrete a protein... That our friend Harvey likens to milk. 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. 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, I'm going to 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. 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, wait, wait. Can I just ask, like, 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 in Seattle, Washington. Radiolab 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 Simons Foundation initiative dedicated to engaging everyone with the process of science.
WNYC Studios is supported by Zuckerman Spader. Through nearly five decades of taking on high-stakes legal matters, Zuckerman Spader is recognized nationally as a premier litigation and investigations firm. Their lawyers routinely represent individuals, organizations, and law firms in business disputes, government, and internal investigations and at trial. When the lawyer you choose matters most. Online at Zuckerman.com.
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I'm Maria Konnikova. And I'm Nate Silver. And our new podcast, Risky Business, is a show about making better decisions. We're both journalists whom we light as poker players, and that's the lens we're going to use to approach this entire show. We're going to be discussing everything from high-stakes poker to personal questions. Like whether I should call a plumber or fix my shower myself. And of course, we'll be talking about the election, too. Listen to Risky Business wherever you get your podcasts.
Lulu. Molly. Heather. Becca. Radiolab. 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. Well, this came as a total shock to me because after all, the thing that... So basically the story we told then is that before placentas, all animals that would become mammals laid 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... Long, long ago, some ancient mammal ancestor got a virus... A virus-infected...
an ancient proto-mammal and changed its DNA so that eventually, many generations later, the eggshell 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 eutherian 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. 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 five goes by, then week six, week seven, the embryos growing eyes, ears, bones. It has a heart, kidneys, liver. 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 of tricks up its sleeve. Specifically, one trick called PP-13. 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 analogy here, PP13 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 PP13 attracts the entire police force, SWAT team, everybody of the mother's immune system. And while the whole police force is over there dealing with the PP13, the placenta's...
Digging claws bust through. And blood fountains into the placenta. It's bathed in all these nutrients and goes, buffet time. Let me see what I need. As the mother's blood starts rushing into the 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 placental lactogen, which sort of hijacks the mother's digestive system. 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 going to force her body to start pumping more blood into me, into the fountaining system. And this is a condition we call preeclampsia. Preeclampsia is vaginitis.
Very, very scary. And it's basically when the mother's blood pressure spikes so high that she can actually die. Whoa. 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. Yeah.
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 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 one in his lab. All right, 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 organ-y. It's kind of bloody, isn't it? It's so bloody. And so I'm going to open the Ziploc bag. Oh my God. It's so bag-like.
It's sort of bluer than I thought. It also kind of looks like raw meat, like you would making a hamburger or something. It is raw meat. So I'm going to pick it up and see how heavy it is. So I grabbed the placenta. It's kind of 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 it's got um 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 all it's like hard and spots and soft and 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, you know, 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 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. 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 camaraderie and a peace of sorts between
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 sort of way that I've started seeing it as the first parent.
Yeah, I don't know. I feel almost like I'm going to cry. It feels sort of 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?
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 burying the placenta all over the world. In various African cultures, in Native American culture. In Hawaii. French Polynesia. In Aotearoa. Tahiti. Vanuatu. And where she's from. Born and raised in Guahan.
in the Marianas. 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.
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
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 let you? 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? I was like, okay, I need something to remember my baby's placenta with 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 thing that I can do is take my baby's placenta home with me.
The only consolation I had really was maybe this will be different next time around for my daughters. And this placenta was delivered yesterday? Monday, actually. Monday late afternoon. Monday late afternoon. So there's a little cute baby someplace who is happy and alive because of this placenta. We got to send that family this podcast. Yes.
I'm sure we can't know who they are, Hip Hop. We can't know who they are. That's part of the reason we have the placenta. But let's thank them anyway. Thank you. In a more spiritual way. Yes, we will thank them spiritually. This episode was reported by Heather Radke and Becca Bressler and produced by Becca Bressler and Pat Walters with help from Matt Kilty and Maria Paz Gutierrez.
Special thanks to Diana Bianchi, Julia Katz, Sam Bajati, Celia Bardwell-Jones, and Hannah Ingraham. Special thanks also to my placenta for getting me here. Thanks. Thanks to the placentas 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. All right, that'll do it. Bye. You want half of the cookie?
Yeah. You have to do what mommy says. Then you gotta repeat what I say, okay? Right. Radiolab was created by... Radiolab was created by...
CZ Luxembourg is our executive producer. Producer. Is it Anne? No, not yet. Dylan Keith, a rector, a sound design. Is it Deanne? Nope. Howard, Beth, Luce, Simon, Alex, Geraint, Bloom, Rebecca, Blasler, Rachel, and...
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Good job. Good job.
