Background <p>Umbilical venous catheters are frequently used when treating premature and sick newborns, to provide central access to medications, fluid, and nutrition. Pleural, pericardial, and intra-abdominal effusions are rare but can be fatal complications in newborns after umbilical catheterization. This is the first reported case of simultaneous pericardial, pleural, and intra-abdominal leakage of parenteral nutrition from a properly placed umbilical venous catheter.</p> Case presentation <p>We present a case of a preterm infant of Northern European descent, born at gestational age of 29 weeks, with a birth weight of 890 g. She received a properly placed umbilical venous catheter shortly after delivery. On day 4 she became critically ill with respiratory failure and required ventilator support for 5 days. She was also hypotensive and received vasopressor treatment for 2 days. Owing to kidney failure and hyperkalemia, she required dialysis treatment for 6 days. She was diagnosed with pleural effusion on the right side, pericardial effusion, and intra-abdominal effusion. The drained effusions were biochemically analyzed and were found to be consistent with parenteral nutrition. After the effusions were drained, she remained hemodynamically stable and was discharged from hospital at 2 months of age. At discharge, her creatinine level was ~100 µmol/L, requiring outpatient follow-up. A cerebral ultrasound and neurological examination at term were normal.</p> Conclusion <p>Although rare, clinicians should remain vigilant for effusions involving pleural, pericardial, and abdominal spaces, even when umbilical venous catheter placement appears correct. Early recognition and intervention are critical to improving neonatal outcomes.</p>