Of all placental mammals, handicaps are the tiniest in comparison to their mother.

在所有胎盘哺乳动物中，与母亲相比，残疾是最小的。

This is our best guess at what the first placental mammal looked like.

这是对第一种胎生哺乳动物外貌的最好猜想了。

Tissue refers to placental fragments retained in the uterine cavity.

Tissue指的是胎盘组织部分残留在子宫腔中。

It's then carefully removed to ensure that there are no placental remnants left in the uterus.

然后慢慢移除，确保胎盘遗留物不会留在宫腔。

Therefore, you need to get your oxygen from the mother's placental blood flow and all that stuff.

因此，你需要从母亲的胎盘血流和所有的东西中获得氧气。

Apparently, her fall caused a placental abruption, where the placenta separates from the uterus. -Oh, my god.

很明显，她的跌倒导致胎盘破碎，胎盘和子宫已经分离了。-天哪。

But you have an early placental abruption.

但你过早出现了胎盘早期剥离。

But in 1960, many experts believed that the placental barrier shielded a fetus from harm.

但在 1960 年，许多专家认为胎盘屏障可以保护胎儿免受伤害。

That's because, typically, the larger a placental land mammal is, the longer its pregnancies are.

这是因为，通常情况下，胎盘陆地哺乳动物越大，其怀孕时间就越长。

The three modern mammal groups -- the placentals, marsupials and monotremes -- all made it.

三个现代哺乳动物群——胎盘 动物、有袋动物和单孔动物——都成功了。