gestation

raskausaika, tiineys

kypsyminen, kehittely The period of time during which an infant animal or human physically develops inside the mother's body until it is born.
The process of development of a plan or idea.
1900, Sigmund Freud, The Interpretation of Dreams, Avon Books, (translated by James Strachey) pg. 149:

It was to a conversation with another friend who had for many years been familiar with all my writings during the period of their gestation, just as I had been with his.