What happens if a pregnant druid wildshapes?

Sorry in advance, using Google Translate... Also, I'm just learning what DnD is.

What happens if a pregnant druid wildshapes?

Does the fetus magically transforms into the fetus of the animal the druid transformed into or it stays the same? Or what if the druid wildshapes into a bird? Is the baby an egg now?

If the baby stays the same, what happens if the druid wildshapes into a spider, for example? Does the druid explode?

And if the druid gives birth while in wildshape and a wolf is born, for example. When the druid returns to his original form, does the baby return as well or does it stay the same?