Is there a specific word to describe the duration before due date?

I'm trying to find a word to describe the time period before a workflow/process should be completed.

Solution 1:

From Oxford Dictionaries online...

lead time - the time between the initiation and completion of a production process

(Pronounced "leed", not "led", obviously!)

Solution 2:

Gestation from Mirriam-Webster:

1: the carrying of young in the uterus (see UTERUS sense 1) : PREGNANCY

2: conception (see CONCEPTION sense 3) and development especially in the mind

Example from same link:

The book has been in gestation for a long time.

This comprehends the entire time period between conception (literal or metaphorical) and delivery.