Because it is growing in it's mothers uterus and fully developing parts of the body.
About 9 months
Giraffes give birth like any other mammal: the baby comes from the uterus down through the vagina. The only difference is that a giraffe is very tall, so the baby has a long way to drop before it lands on the ground (or in April's case, in the soft hay of her enclosure).
around 9 months
A baby Orca is in it's mothers tummy for 8 Months before birth.
If a baby is born naturally, often the doctor or nurse will rest the baby on top of your belly. This stimulates your uterus to expel the placenta, etc. Other times you or your baby may need an intervention and a lot will depend on what is needed. In most cases you are handed the baby within 5 minutes of birth.
about 12 years
Horses have a gestation period (how long it carries its baby in its uterus) of, on average, 11 months, or about 340 days.
A baby goat will walk after they are born on the same day/night. It usually takes a couple of hours after birth before they stand and attempt walking.
I would name it before preschool, because in preschool everybody is writing their name...
After about 36 to 38 weeks of pregnancy, a baby is well-developed enough to survive outside the womb. In the process called "labor" the uterus contracts, pushing the fetus down the birth canal. In a period of from minutes to hours, the baby emerges and takes its first breath of air. Watch the video in the link provided below and you will know exactly how a baby is born.
A healthy infant human can take upto nine months in development before it is ready for birth.