Becca Bressler

And that's the story we're going to tell you.

And that's the story we're going to tell you.

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.

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.

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.

You know, the pregnancy is a little bit genetically the mom, but also a little bit the dad.

You know, the pregnancy is a little bit genetically the mom, but also a little bit the dad.

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.

Which, for the mother's body, is not normal.

Which, for the mother's body, is not normal.

Melissa Wilson, geneticist at Arizona State. We need to get rid of not-self.

Melissa Wilson, geneticist at Arizona State. We need to get rid of not-self.

Melissa Wilson, geneticist at Arizona State. We need to get rid of not-self.

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.

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.

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 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.

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.

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.