Is there any one of these documented conditions? - like ,
Rh disease, Twin to twin Transfusion Syndrome, Fetal heart failure causing pericardial effusion, Congenital heart disease and cardiac arrhythmias, cystic hygroma, cyst formed from embryonic lymph tissues,infection or diaphragmatic hernia.
If you cannot find any of these documentation,
I would suggest for 746.9 and 760.3 for an underlying maternal condition,
classifiable to 390-459,490 - 519, 745-748.