There are several restrictions on the ability to marry.  First off you must be 18 years old to marry but the court may grant a marriage license to a 16 or 17 year old if the parents consent to it in writing OR a district court judge finds that the parties are capable of assuming the responsibilities of marriage and that marriage would be in the best interest of the parties.  The judge can grant the right to marry even if the parents disagree, but this is rare.  Pregnancy alone may not be enough to get a license.  (Also Iowa does not recognize gay marriages.)  Iowa is bound by the U.S. Constitutional provision that requires Iowa to recognize other states laws and give them “full faith and credit.”  This means that if Missouri allows a 15 year old to get married then Iowa must recognize the couple as married.  Iowa would not have to recognize a marriage from another jurisdiction if it violated “public policy”, such as a gay marriage.