Hello, The outcome for the baby born with mild fetal hydronephrosis is good. For those with severe condition, excellent perinatal and postnatal care is needed. Also, severe conditions are usually associated with a chromosomal anomaly. Other associated renal anatomical defects also must be looked for. Soon after delivery, sonogram should be done for all infants. Immediate imaging is needed in the severe cases. Management is accordingly planned. Pediatric urologist should take care of complications in severe fetal hydronephrosis cases. Hope this helps.