ICD-10 Chapter 16-Conditions Originating in the Perinatal Period

Can anyone help me with an ICD-10 question. We are a pediatric practice and a lot of times a patient is seen that say was premature at birth and some of the codes from this section still apply for the actual cause of additional problems. Every time one of these codes appear on a claim for a patient that is over 28 days old, the claim will reject. They are billed out as secondary codes, not primary. Any suggestions on which codes to use for this kind of a situation?