These 'marriages' will not last a year, I assure you. Teenagers are in a phase of constant change, the couple will get bored of each other in no time. How will they feed and take care of a child?
You assure me that a marriage mostly against her say,will be over in a year! Well I see issues with that statement because...
She most likely has no say in the marriage.
She is more a prisoner than a equal partner.
She is not of a developed mind to make such commitments
If they allowed this,it would open up a black market for child trafficking under the guise of marriage.