You can not compare pregnancy to addiction, two entirely different things.
You can not compare addiction to cancer, again two entirely different things.
I do believe that anyone who gets married, and believes in the vows of marriage are still vunerable to disappointment in their spouse , if you believe that vows are holy and given before God, and then believe that because of those vows you need to stay in a marriage no matter what, then you also believe that God gives you no out, or God intends that you suffer whatever is suffered because of a spouses addiction.
Addiction has nothing to do with God, or vows, addiction , for me, does not fit into the discussion.
We as humans have free will.
It seems I often read here , how bad those of us who have left are, because we left someone with a disease. The difference between this disease and cancer for instance, is that the healer of this disease is solely the person who has it, there is no doctor that can get an addict to want to quit. It is apples and oranges.
I was in a relationship with and A whose disease was progressing to the point of no return, I was constantly under attack, for me it was leave or continue to be attacked, I spent five years trying to help someone that didn't want help, that loved booze more than anything in the world, he would do or say anything when drinking, the most hurtful evil things , things I could never even come up with, I thought God put me there to make his life better, God had a different plan, I had to be done, and leave, so God could do his work in his own way and in his own time.
Addiction is war, hopefully you husband will keep fighting, I hope you are neever faced with the decision many here have faced. And I mean that, the cure for you husband addiction is up to him, vows play no part in addiction.