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.

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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".