**2.5 Non-pregnant women**

Today there is international consensus that specific gynecological problems can be caused by a niche:

As the main symptom, abnormal uterine bleeding, e.g. postmenstrual spotting, results from a retention of menstruation blood in the indentation of the myometrium [14]. Nearly 30% of women with a niche report spotting compared to only 15% without a niche within 6–12 months after a CS [11]. An insufficient contractility of the myometrium seems to be the main reason [1]. Also the size of the niche is important since women with larger niches are reported to have more severe bleeding issues [2].

Several studies describe dysmenorrhea, dyspareunia or even chronic pelvic pain as further symptoms of a niche [6, 11]. The reason for pain during the menstruation bleeding might be found in the myometrium's distension caused by the accumulating blood.

Importantly, the presence of a niche may affect fertility: the accumulation of blood in the niche deteriorates the quality of cervical mucus, potentially inhibiting

#### *Current Topics in Caesarean Section*

sperm transport or referring to an impaired implantation of the embryo [15]. It has been shown that the repair of scar defects is able to restore fertility [15].

Therefore, a symptomatic niche can mimic frequent gynecological issues like endometriosis or pelvic inflammatory disease and should be considered as a differential diagnosis.

Addionally, an elevanted risk for intervention-related complications during a curettage oder device placement should be considered in the presence of a niche.

#### **2.6 Pregnant women**

In contrast to non life-threatening problems in non-pregnant women, the presence of a niche may derive in major complications during pregnancy. There is an important risk of a CS scar ectopic pregnancy (CSP) at the site of the niche [16] (**Figure 8**). CSP occur with an overall incidence of 1: 1800–1: 2216 pregnancies [17]. Even in earlypregnancy, CSP treatment can be associated with severe hemorrhage [18].

#### **Figure 8.** *Cesarean scar ectopic pregnancy.*

**Figure 9.** *Intraoperative demonstration of placenta percreta.*

*Prevention of Cesarean Scar Defects: What Is Possible? DOI: http://dx.doi.org/10.5772/intechopen.97618*

**Figure 10.** *Uterine rupture after vaginal delivery in a patient with a former Cesarean section.*

In most cases, CSP results in morbidly-adhaerent placenta like placenta accreta, increta or percreta [19]. Short- and longterm complications can be detrimental [20] (**Figure 9**).

Uterine rupture during pregnancy and labour is a rare but life-threatening sequeleae both for the mother and the fetus [21] (**Figure 10**). It appears conclusive that a thinner myometrium increases the risk of a rupture. Unfortunately, no cutoff value of myometrial thickness was defined as a reliable predictor of uterine rupture. A RMT > 2.1–4.0 mm and LUS thickness between 3.1–5.1 mm were described as strong negative predictive values for uterine rupture. A RMT of 0.6–2.0 mm was considered as a positive predictive factor for uterine rupture [22].

Since the clinical consequences of niches can not be exactly predicted, the prevention of niches formation is crucial. Insights into the pathogenesis of niche development will allow the initiation of preventative approaches.
