Why Do Niches Develop in Caesarean Uterine Scars? Hypotheses on the Aetiology of Niche Development

Abstract

Caesarean section (CS) results in the occurrence of the phenomenon '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 CS. Using gel or saline instillation sonohysterography, a niche is identified in the scar in more than half of the women who had had a CS, most with the uterus closed in one single layer, without closure of the peritoneum. An incompletely healed scar is a long-term complication of the CS and is associated with more gynaecological symptoms than is commonly acknowledged. Approximately 30% of women with a niche report spotting at 6-12 months after their CS. Other reported symptoms in women with a niche are dysmenorrhoea, chronic pelvic pain and dyspareunia. Given the association between a niche and gynaecological symptoms, obstetric complications and potentially with subfertility, it is important to elucidate the aetiology of niche development after CS in order to develop preventive strategies. Based on current published data and our observations during sonographic, hysteroscopic and laparoscopic evaluations of niches we postulate some hypotheses on niche development. Possible factors that could play a role in niche development include a very low incision through cervical tissue, inadequate suturing technique during closure of the uterine scar, surgical interventions that increase adhesion formation or patient-related factors that impair wound healing or increase inflammation or adhesion formation.

Uterine caesarean closure techniques affect ultrasound findings and maternal outcomes: a systematic review and meta‐analysis

“…Finally, a niche and associated intrauterine fluid accumulation may theoretically hamper implantation or sperm penetration and therefore negatively influence pregnancy rates. 44 Our analyses indicate that RMT and a niche may be intermediates for long-term outcomes but future studies are needed to evaluate this in larger studies measuring these outcomes. To facilitate future meta-analyses, we suggest performing ultrasonographic evaluation after CS in a standardised way.…”

Preliminary report on the use of a levonorgestrel intrauterine system for the treatment of intermenstrual bleeding due to previous cesarean delivery scar defect

“…Abnormal uterine bleeding associated with previous cesarean delivery scar defects (PCDS) has become a serious problem due to the increasing number of cesarean sections being performed. 1,2 The rate of cesarean sections has risen to around 35-37% in Taiwan in the past decade, 3 which indicates the possible rise of prevalence of PCDS. 4 One previous systematic review reported that the prevalence of PCDS was between 56% and 84% using sonohysterography in women with a history of cesarean section.…”

The prevalence and risk predictors of cesarean scar defect at 6 weeks postpartum in Shanghai, China: A prospective cohort study

“…8,9 Until now, most CSD risk factor studies focused on surgery-related factors of wound healing, such as incision location, adhesions, incomplete uterine closure, uterine suture technique-like single-layer vs double-layer uterine closure, or including vs excluding the endometrial layer at CS. [10][11][12] However, scant attention has been paid to patient-related factors, such as coagulation and presence of infection, which may potentially affect wound healing.…”