Pregnancy is the state of being pregnant, the time a woman grows a baby in her belly. For humans, pregnancy lasts about nine months, during which time the mother might want a chocolate chip and pickle sandwich. Get her one.
Before a mother bear gives birth to a cub, or a mother cat has kittens, she goes through pregnancy. In humans, pregnancy is a time to prepare for a new baby while the mother-to-be does things like take special vitamins and choose a doctor or midwife to assist with the upcoming birth. Bears and cats just go for it. Pregnancy comes from the Latin praegnans, "with child" or "before birth," from prae-, "before," and gnasci, "be born."