Gestation

Gestation is the carrying of an embryo or fetus inside the uterus of a female mammal. In mammals that undergo a pregnancy, they can have one or more gestations at the same time, resulting in multiple gestations (such as twins).

For example, female dogs usually have multiple ovulations in a single estrus cycle, and, when the ova get fertilized, the animal gestates multiple offspring in one single pregnancy.

The time interval of a gestation is called a gestation period and the length of time they have spent developing in the uterus is the gestational age.