I won't argue this much because there are cultures that permits for pregnancy before marriage, while we have a larger percentage on those that only advise after marriage, but ideally, we should have this done in marriage after doing the normal traditions as required by each custom, this goes along with the blessing to abounds in the marriage and make it more fruitful for them both to enjoy ad they planned to live together forever.
I see no difference, provided the man would take the girl to the alter after getting her pregnant then no problem. A good percent of married people got their spouse pregnant before Marriage. I've known of couples that wedded after a year of living together. Intercourse is a thing of consent, aside that it's an abuse. So, if both sides consent on having a baby before going for parental blessings, then that's what should make the union work. One person's disagreement to that can ruin the relationship.
A align with Accardo the more. I see no difference if the couples are truthful to themselves. If procreation is the only reason for marriage, then getting a woman pregnant before marriage is the right thing to do. But if marriage is first seen as a beautiful thing before children starts coming, this might not be a big problem to the couple. I understand that in my country, any marriage without a child always faced alot of pressure from relatives and friends.
Op, it depends on what the couples want. Do they actually want to be having children from the first year of their marriage, it's okay the lady gets pregnant first. But if they want children coming maybe after 2 or more years of marriage, there's no need getting the lady pregnant first. You see that it is purely subjective.