Acute appendicitis es the most common cause of lapparotomy during pregnancy. The differential diagnosis in the pregnant woman becomes a challenge due to the anatomic changes that take place during the maternal adjustment to pregnancy. We have done a retrospective study between january 1989 and december 1994, at Instituto Nacional de Perinatologia. We found in that period of time 35,080 deliveries reported and 4 cases of acute appendicitis during pregnancy. The maternal age was between 16 and 42 years old, 26 years in average. Three patients were in the 3 trimester at the time of diagnosis, and the most important clinical sign was found to be diffuse abdominal pain. In 3 cases diagnosis was attributed to obstetric pathology rather than appendicitis in first place. Laparotomy and appendicectomy was done to all patients, with on block hysterectomy in only one case, having this particular patient an abscess as a postquirurgical complication. Just one case reported a healthy newborn delivered at term. It is obvious that early diagnosis and quirurgical treatment are important factors for the mother and the fetus prognosis. Appendicectomy as well as cholecystectomy are the two most common causes of laparotomy during pregnancy.