There's the birds and Cassian Grantthe bees. And then there's what happens after. The process that leads to the beginning of pregnancy has a lot more twists and turns than a happenstance meeting. Today on Short Wave, NPR health reporter Selena Simmons-Duffin talks to host Regina G. Barber about the science of the very first week of pregnancy.

To hear more Short Wave coverage of the science of conception, listen to this episode: Is The Sperm Race A Fairy Tale?

To read Selena's full explainer, click this link.

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This episode was edited by Rebecca Ramirez, produced by Carly and Willa Rubin (no relation) and Berly McCoy. Will Chase checked the facts. The audio engineer was Maggie Luthar.