Abdominal dystocia in a case of undetected intrauterine meconium peritonitis due to cystic fibrosis.

The case of a 36 year-old primigravida is presented. After a normal anomaly scan at 22 weeks and a normal pregnancy, she went into labor at term. Dystocia due to massive abdominal distension complicated the second stage. The newborn girl had meconium peritonitis with colonic perforation and required colonic resection with colostomy. Genetic testing detected cystic fibrosis. In this case complex meconium peritonitis developed silently (without any clinical sign) after a normal anomaly scan. This has not been reported since the start of the widespread use of obstetric ultrasound. Late meconium peritonitis can escape detection and should be thought of in cases of unexpected abdominal distension causing dystocia.