BACKGROUND Surgical site infection (SSI) is one of the most common complications after cesarean and causes much burden on the mother as well as the health care system. SSIs are defined as infections of a surgical site up to 30 days after surgery. Ultrasonography of the surgical site may be a helpful tool to detect its complication. With this background, the following study was planned to evaluate the clinical significance of sonographically detected fluid collections and post-operative maternal morbidity following cesarean section (CS) and identify risk factors associated with their formation. METHODS This prospective observational study was conducted at the Department of Obstetrics and Gynecology, Lala Lajpat Rai Memorial Medical College, Meerut. A total of 1000 women, who had undergone CS were included. Sonographic examination of the cesarean site was done on the 3rd or 4th postoperative day to look for any fluid collection in the parities or pelvis. All cases were followed on the 8th postoperative day and finally on the 30th postoperative day to look for any SSIs i.e. surgical wound problems like wound infection, induration, and discharge from a surgical wound, or even wound dehiscence and postoperative morbidity.  Results: Out of the total cases (1000), abdominal wound fluid collection was noted in 490 (49%) women after CS. Thirty-two patients were lost to follow-up, so 458 patients were followed, of which collection was septated or loculated in 62 (13.6%) and diffused in 396 (86.5%). Out of 62 loculated and 396 diffused cases, 21 (33.87%) and 20 (5.05%) cases reported surgical site abdominal wound infection and needed resuturing, respectively and it was found to be highly significant (p<0.001). CONCLUSIONS Post-operative fluid collections are common after CS. But it is the pattern of the fluid collection that determines post-operative wound infection and morbidity. Thus ultrasound of the cesarean site may be an important tool to detect surgical site wound complications earlier and to decrease postoperative morbidity.