A principal, under the laws of agency, is able to ratify a contract made on the principal’s behalf by an agent that had no authority. That only applies where, at the time the agent entered the contract, the principal existed and had contractual capacity
You can’t enter a contract on behalf of your unborn child for the child (after birth) then to ratify that contract because at the time you entered the contract, the child did not exist as a contractually-able person
Now, instead of a child, put an unincorporated entity into the child’s position