3 cases of antenatal intestinal perforation so far , we have entertained in our NICU. All term newborns with symptoms like abdominal distension and vomiting on day 2-3  of life, imaging done(X-ray and USG abdomen ) and revealed NEC like picture stage 3 with advance presentation . interestingly, newborn were not so sick clinically. one of them were diagnosed in antenatal period as some pseudocyst around live or pancreas through fetal MRI. Surgical interventions done  and all are doing well during follow up. Biopsy of intestinal segment around perforation doesn't reveal  any significant pathology.

 

I have also similar cases, knowing the surprise, first looking at abdominal x-ray and then looking at the baby seeming rather well!

I found a few case reports published, see here https://pubmed.ncbi.nlm.nih.gov/26034708/ and here https://pubmed.ncbi.nlm.nih.gov/12900715/