Background The authors report the first case of antenatal perforation of fetal appendix, which presented as isolated ascites and polyhydramnios at 28-week gestation.

Case 28-year-old woman, G2 P0+1, non-consanguineous marriage, with a positive blood group and a normal mid-trimester scan, was referred at 28-week gestation with sudden increase in symphsio-fundal height measurement. Antenatal Ultrasound showed polyhydramnios, and fetal ascites with no hydrothorax, pericardial effusion or soft tissue calcifications. The umbilical artery, middle cerebral artery and ductus venosus Doppler were all within normal range. All immunological and infection screening were negative. Amnioreduction and karyotyping was performed and was normal. She went into spontaneous labour at 33 weeks and delivered a live male baby 2.5 kg in weight with normal Apgar score and cord gases. The baby was admitted to neonatal intensive unit. Abdominal examination revealed a mass to the right side of the umbilicus, confirmed on abdominal x-ray. He underwent laparotomy at age of 2 days which showed a necrotic perforated appendix with meconium pseudo cyst, confirmed on histology.

Conclusion Isolated fetal ascites with otherwise normal ultrasound and no hydrops carries a good prognosis. Conclusive aetiologic diagnosis requires careful postnatal work up. Perforated appendix needs to be considered as a possibility.