Why does the fetal circulation need to be special, what does the oxygen dissociation curve look like?

为什么胎儿循环这么特殊，氧解离曲线是什么样子的？

Anyway, this one, what does the oxygen dissociation curve for hemoglobin look like, comparing maternal versus fetal.

无论如何，这个，血红蛋白的氧解离曲线是什么样子的，比较母亲和胎儿的。