Introduction
Meconial peritonitis (PM) is a localized or generalized peritonitis, aseptic, chemical or strange body; product of meconium steps to the peritoneal cavity and is correlated with prenatal perforation of the digestive tract. It occurs in 1 in 30,000 newborns. Prenatal ultrasound diagnosis improves perinatal outcomes, the most frequent finding is ascites. PM requires urgent multidisciplinary treatment, most of cases needs surgical resolution.

Objective
To present an infrequent pathology, which requires a high degree of diagnostic suspicion to grant a specific and timely perinatal management.

Clinical case
Pregnant 29 years old woman without morbid history, 36 weeks of controlled pregnancy. Ultrasound control shown fetal ascites. He is hospitalized at high obstetric risk, ruling out metabolic and infectious pathology. At 37 weeks by emergency caesarean section, is obtained a baby boy with abdominal distension and hepatomegaly.  In exploratory laparotomy there are undamaged intestinal handles. In re intervention it is noted herniated perforated distal ileum, ostomy is made. Patient evolves favourably and is discharged.

Discussion
It is essential consider PM within the differential diagnoses of fetal ascites. An opportune diagnosis improves the perinatal results and could avoids possible complications.

Keywords: Diagnosis, treatment, Meconium peritonitis.