What is the method of reproduction in mammals?

Reproduction in most mammals involves internal fertilization by the male of one or more eggs in the female. The most common method of delivery is the placental form, where fairly well-developed offspring develop in the uterus and are born live. The other two delivery methods are

1) the marsupial, where a less-developed offspring leaves the uterus through the vagina and travels to a pouch where it completes its maturation.

2) the monotreme, where the fertilized embryo is encased in an egg, as with most birds and reptiles, and develops mainly there, then hatches in a burrow where it begins to suckle on the mother.