In the past decade several articles have described a defect that can be seen on ultrasound at the site of cesarean delivery scar, known as a 'niche' .An incompletely healed scar is a long-term complication of cesarean delivery and is associated with symptoms such as postmenstual spotting, dysmenorrhoea, chronic pelvic pain dyspareunia and subfertility. This study aimes to evaluate the prevalence of niche in a large cohort study after long term follow up since operation, and characterize the risk factors for its development and for symptoms to appear.

As the rate of cesarean deliveries continues to increase, concern regarding the association between delivery by cesarean section and long-term maternal morbidity has been growing . In the past decade several articles have described a defect that can be seen on ultrasound at the site of the cesarean delivery scar, known as a 'niche' .A 'niche' describes the presence of a hypoechoic area within the myometrium of the lower uterine segment, reflecting a discontinuation of the myometrium at the site of a previous cesarean delivery . An incompletely healed scar is a long-term complication of cesarean delivery and is associated with symptoms such as postmenstual spotting, dysmenorrhoea, chronic pelvic pain dyspareunia and subfertility.

The reported prevalence of a niche in non-pregnant women varies depending on the criteria used to define a niche, the time of evaluation since operation, method of detection, and study population. Osser et al. used the definition 'any visible defect' , Bij de Vaate et al. used 'any indentation of at least 1 mm and van der Voet used a cut-off level of 2 mm, however, consensus on the exact cut-off levels is lacking. As approximate evaluation to the operation, the prevalence reported is higher, as early scanning may facilitate the recognition of the location of the caesarean delivery scar in the uterine wall due to incomplete scar healing, with no definition of the most appropriate time since operation. Commonly used methods to evaluate the presence of a niche are trans vaginal ultrasound, sonohysterography and hysteroscopy with detection rate of approximately ~50% of women with previous cesarean section in all methods with no definition of the gold standard.

The aim of this study in to evaluate the prevalence of niche in a large cohort study after long term follow up since operation and characterize the risk factors for its development and for symptoms to appear.

Inclusion Criteria:

• Women after cesarean delivery
• Minimum interval of 3 months since operation

Exclusion Criteria:

• Uterine scar other than low segment cesarean section ( s/p myomectomy, S/p T scar)
• Morbidly adherent placenta during pregnancy
• Cesarean hysterectomy
• Uterine anomaly