Can we change the future?

I am intrigued by a phenomena I can’t get my mind around:
My brother in law and his wife recently had their first child. You have to understand the great lengths that they went through for this to happen. After months (maybe years) of trying very hard, they almost gave up. But they decided to try a very expensive procedure of invetro fertilization. 15 or 30 thousand dollars later, they now hold Abigail in their arms.
Was Abigail planned by God since the beginning of time? Did he know her by name? What if Nate and Becca didn’t do invetro fertilization? Did their effort make a difference on who will literally be around for all of eternity? It seems so.
God is sovereign, certainly, over who will be born. But he has somehow given us the mind-boggling ability to procreate, or not procreate! Certainly, he gives us desires that should lead to multiplication. But it is possible to use contraceptives to the degree that no children are born, even though this is contrary to what he has willed in us.
If this is true in the natural sense, isn’t it also possible in the spiritual sense? He works in us to will to produce spiritual fruit, leading to spiritual multiplication. This is the natural tendency. But somehow, mysteriously, he also seems to have ceded over to us the choice to be involved in the Work, or to live selfish lives. Will we, or can we, spiritually procreate? Will others be in heaven, or not be in heaven, due to us? God forbid that he would give us that substantial of an impact. Unfortunately, though, it appears that he has. What are the implications for my neighbors? I am just wondering….