about the length of pregnancy (gestation)

one would think that after 9 months, a human baby would spring out, fully-formed and be capable of any and everything. As we know, that is not the case.
Why is that so?
I reckon it;s so that the prospective father can have three months for denial (that well-known river in Egypt), three months for the concept to sink in (takes time), and three months to do everything he ever wanted to, never got around to doing, and won't have a chance to do.
Only problem being that in the last three months, no way is She-who-must-be-obeyed going to let him....