Answer:
(1) The financial needs and resources of the child;
(2) The financial resources and needs of the parents;
(3) The standard of living the child would have enjoyed had the marriage not been dissolved;
(4) The physical and emotional condition of the child, and the child's educational needs;
(5) The child's physical and legal custody arrangements, including the amount of time the child spends with each parent and the reasonable expenses associated with the custody or visitation arrangements; and
(6) The reasonable work-related child care expenses of each parent.
RSMO 452.340
In July, a law was passed allowing for a post order challenge of paternity within two years of the establishment of the order.
see link