Solution 1: Death sentence for the baby if discovered immediately and compense for those who report the crime of birth to the authorities. Parents get sterilized.
Solution 2: Since new, approved births, are supposed to be registered not just with a keyboard or a pen-written register, all new babies' DNA is supposed to be registered in a database and the baby provided with a unique chip. Lack of said chip will prevent any baby that escapes authorities to access all services. No food, no water, no housing, no medicals, no schooling nothing. Parents, their friends and relative will be unable to buy stuff for the baby because they must submit the baby's chip for approval.
Solution 3: even if, and it is possible after point 2, baby should make it into an adult by staying under the radar, there's a death sentence hanging over the adult's head and, retroactively, over everyone who helped the baby back then. This will be imprinted via all communications media to all social strata, from the rich to the poor. The 'citizen X' will live with the knowledge that the slightest mistake will cause the death of many. And everyone in the circle who protected the baby back then will probably break down under pressure.