Hmmm tricky issue...
The only thing I will say is this, my husbands father got his mom pregnant when she was 16 and he was 21, they were both raised Christian. Thankfully, his father had his own house and job when it happened so he wasn't exactly a beat up loafer eating fruitloops in Star Wars pjs in his Moms basement. The most wonderful thing happened, he stepped up and took on his shoulders the consequences and responsibility of what he had done, and went on to have three more children and my father and mother in law (despite some hard times throughout the years) are still married and enjoy each other. However imperfect he has been, my husband holds his father in the most highest regard and respect for what he did.
I believe that many churches who force young people to get married do it with the best intentions and hope for an outcome like above, also in part because it keeps the woman from poverty and prevents the involved child/children from missing out on father involvement (which has a huge impact on their mental and social development). Partners who get bitter and divorce do so because they don't view marriage as a covenant, thats not the fault of whatever church organised the marriage. Its not a sin to stay together because of children. Sure its not the best scenario either, but research on child health supports it, while the marriage is intact there is always hope for someone wiser and godly to step in and help