Chapter 2 presents a retrospective cohort study comparing fertility outcomes between women with a previous CS and those with a previous vaginal delivery. We found significantly lower live birth rates, ongoing pregnancy rates, and clinical pregnancy rates in women with a prior CS. The lower clinical pregnancy rates per embryo transfer indicate that implantation is hampered after a CS. Its relation with a possible niche needs further study. In chapter 3 we present our hypothesis on various explanations for post CS niche-related impaired fertility. The hypothesis are divided into three categories 1) accumulation of intrauterine fluid, causing altered immunobiology or increased inflammation and distorted contractility of the uterus may impair implantation; 2) accumulation of mucus in the niche that may impair sperm penetration and 3) niche related gynaecological symptoms interfering with the opportunities to conceive. Chapter 4 presents the results of a prospective cohort study investigating the effect of Ultrasound Speckle Tracking on subendometrial wave patterns in women with (large) niches after previous CS compared to controls without a Cesarean scar. This study demonstrated that subendometrial contractions were disrupted in women with a niche, potentially contributing to postmenstrual spotting, dysmenorrhea, and reduced implantation rates. Chapter 5 presents the results of a prospective cohort study (LapNiche study), in which we studied the effect of a laparoscopic niche resection on niche related symptoms and quality of life and reported the six months follow-up results. The procedure reduced postmenstrual spotting, discomfort due to spotting, dysmenorrhoea and the presence of intrauterine fluid in the majority of women and increased the residual myometrium. Chapter 6 provides long-term follow-up, including reproductive outcomes of the LapNiche study described in chapter 5. Women with a desire to conceive were included, both with and without a history of infertility. We concluded that the reproductive outcomes in women with and without previous fertility problems undergoing resection of a large niche are very promising and quite comparable in both groups Chapter 7 presents a prognostic model for successful laparoscopic niche resection in women with large symptomatic niches. This study shows that a longer pre-operative duration of spotting and a larger volume of the niche are associated with a higher likelihood of symptomatic relief. Identifying predictors of successful laparoscopic niche resection should be an important future field of research, as it will improve the selection of patients who will benefit. In chapter 8 examines changes in residual myometrial thickness (RMT) before and during pregnancy pregnancy in women with and without laparoscopic niche resection and evaluate niche presence. The study found that RMT increased during pregnancy after resection, and there were fewer cases of uterine dehiscence compared to an expectant management group. In general, laparoscopic niche resection is performed to improve gynecologic symptoms. Chapter 9 describes the protocol for the LAPRES study, a randomized controlled trial designed to evaluate the long-term effectiveness of laparoscopic niche resection in improving reproductive outcome.