A human embryo. Humans have a gestation
period of around 9 months
Gestation is the period of development where some animals carry their babies inside their bodies before they give birth. Viviparous animals are animals where the embryo develops inside their bodies, eventually leading to live birth.
Some animals can have more than one embryo or fetus inside their body at the same time. It is the standard method for all mammals except monotremes.
The time between fertilization of the egg (ovum) and the birth of the baby or babies is called the gestation period.
Humans have a gestation period of around 37 weeks or about 9 months and 1 week. Syrian hamsters have a gestation period of 16 days. That is believed to be the shortest gestation period.