Let me take this up from the insight of my culture as an African. We prioritizes marriage as a union to live together and forever affirmatively to bear children and whereas the wife is been unable to conceive, they both begin to worry about which of the partners fault it is which would lead to medical test running to resolve whatever that maybe the problem and if by means all sorts of tests and research has been made and to no avail, the man may have no option than to pick another wife because bearing a biological parent is very necessary in the African culture unlike some cultures that are not bothered about biological children Instead they prefers to adopt.

And nowadays that youths has not been careful about their health especially the abuse of sexuality, both males and females has become fond of drugs intake to support their performance which substance may have reproductive side effects between between both the male and the females organs.
And one of the effective cause of the females being unable to conceive in marriage is the repercussions of abortions during their youthful life when they were single.

So as for me, I will feel the real man having my own biological children and not adoption and so, I would not want to pick a second wife either due to her inability to conceive and with the trends of nowadays that youths has become neglected health wise and only look out to fun, I suggest pregnancy before marriage but if partners has checkmate on themselves and are sure of no negative effects to breach reproduction, it is okay to go marriage before pregnancy because by then, all reproductive fitness is assured in orderliness.