Pregnancy is an amazing phenomenon:

The body adapts to physiological changes in every organ system: the blood volume goes up and the heart's output increases to compensate. The lungs get smaller as the baby grows in the uterus, and respiration increases to get enough oxygen to the body. A surge of hormones leads to changes in tissues and enzymes and basic functions. Everything leads up to the ultimate event...

and then the baby is delivered and somehow everything goes back to normal.

How does the body handle such dynamic plasticity?

What happens when something goes wrong?

Maternal hypertension and a condition called pre-eclampsia is one example of how variability can be lost.

Physiological Changes in Pregancy