In our randomized study, we've examined sonographically 238 first c.s. carried out through Stark technique and 46 traditional repeat c.s. with open peritoneum (284 with open peritoneum), compared to 253 women who underwent a first c.s. with the classic technique and 51 previous traditional c.s. (304 c.s. with closed peritoneum) the aim of our investigation is the sonographic evaluation of patients with open peritoneum and those with closed peritoneum to discriminate the frequency of bladder flap hematomas in the two techniques. The statistical analysis has been conducted with the test of Student considering significant a value of P < 0.05. C.s. with PROM, abruptio placentae, and placenta previa have been excluded from our study. For this reason all the patients of the two groups were examined by transvaginal and transabdominal sonography, on the 3rd and 12th postoperative day, to demonstrate the possible presence of retrovescical collections/hematomas, assuming as sonographic criterion the presence of a fluid or mixed mass on the lower‐uterine‐segment (L.U.S.), of three or more centimetres, clean wall, with reinforcement of distal echoes. It has been observed that in the group with open peritoneum c.s., there were masses of mixed ecostructure referring to hematomas on the 12th day in 9 cases (3.16%), while in the group with closed visceral peritoneum in 48 cases (15.78%) (P < 0.05). Sonography, which is a simple reliable riproducible and low cost technique let us confirm previous experiences made by TAC and MR whic indicate that bladder flap hematomas are usual in post‐c.s. In 39 cases (81.25%), they were collections on the L.U.S. from 3 to 4.2 cm, in 6 (12.50%) from 4.2 to 5 cm (4.16%) and only in one case it was a lateral collection of 6 cm (2.08%) which did not require surgical treatment anyway (the last 3 cases have been observed by MR which which confirmed sonographic findings). In addition in 104 patients (36.61%), there was the presence of a fluid collection in Douglas region due to the amniotic liquid usually not removed according to the Stark technique. Besides in 22 patients (45.83%) the bladder‐flap hematoma was associated with fever (values > 38.5 °C), in this group other causes of febrile morbidity were obviously excluded. The characteristic of these c.s. was a significant intraoperative blood loss, evaluated with a drop in Hb of 3 or more g/dL. On the contrary it was observed a significant differences of the intestinal functionality restarting 8.6 h at c.s. with open peritoneum and 42.7 h (P < 0.05) at c.s. with closed peritoneum but a careful examination confirms that therapid resumption is favoured by regional anaesthesia as regards general anaesthesia, rather than by surgical technique. Subsequently 82 women undergoing the first Stark c.s., have been reoperated with the same technique, with open peritoneum, but not significant differences have been observed in comparison to c.s. with closed peritoneum from a postsurgical adhesion profile. According to the data of literature, peritoneum closure in c.s. lengthens operative time and in some cases favours hematomas on the L.U.S. which increase postoperative morbidity, antibiotics use 2.6 and 4.8 (P < 0.01), length of Hospital staying and costs.