STUDY QUESTION Does a previous Caesarean section affect reproductive outcomes, including live birth, in women after IVF or ICSI? SUMMARY ANSWER A previous Caesarean section impairs live birth rates after IVF or ICSI compared to a previous vaginal delivery. WHAT IS KNOWN ALREADY Rates of Caesarean sections are rising worldwide. Late sequelae of a Caesarean section related to a niche (Caesarean scar defect) include gynaecological symptoms and obstetric complications. A systematic review reported a lower pregnancy rate after a previous Caesarean section (RR 0.91 CI 0.87–0.95) compared to a previous vaginal delivery. So far, studies have been unable to causally differentiate between problems with fertilisation, and the transportation or implantation of an embryo. Studying an IVF population allows us to identify the effect of a previous Caesarean section on the implantation of embryos in relation to a previous vaginal delivery. STUDY DESIGN, SIZE, DURATION We retrospectively studied the live birth rate in women who had an IVF or ICSI treatment at the IVF Centre, Amsterdam UMC, location VUmc, Amsterdam, the Netherlands, between 2006 and 2016 with one previous delivery. In total, 1317 women were included, of whom 334 had a previous caesarean section and 983 had previously delivered vaginally. PARTICIPANTS/MATERIALS, SETTING, METHODS All secondary infertile women, with only one previous delivery either by caesarean section or vaginal delivery, were included. If applicable, only the first fresh embryo transfer was included in the analyses. Patients who did not intend to undergo embryo transfer were excluded. The primary outcome was live birth. Multivariate logistic regression analyses were used with adjustment for possible confounders ((i) age; (ii) pre-pregnancy BMI; (iii) pre-pregnancy smoking; (iv) previous fertility treatment; (v) indication for current fertility treatment: (a) tubal, (b) male factor and (c) endometriosis; (vi) embryo quality; and (vii) endometrial thickness), if applicable. Analysis was by intention to treat (ITT). MAIN RESULTS AND THE ROLE OF CHANCE Baseline characteristics of both groups were comparable. Live birth rates were significantly lower in women with a previous caesarean section than in women with a previous vaginal delivery, 15.9% (51/320) versus 23.3% (219/941) (OR 0.63 95% CI 0.45–0.87) in the ITT analyses. The rates were also lower for ongoing pregnancy (20.1 versus 28.1% (OR 0.64 95% CI 0.48–0.87)), clinical pregnancy (25.7 versus 33.8% (OR 0.68 95% CI 0.52–0.90)) and biochemical test (36.2 versus 45.5% (OR 0.68 95% CI 0.53–0.88)). The per protocol analyses showed the same differences (live birth rate OR 0.66 95% CI 0.47–0.93 and clinical pregnancy rate OR 0.72 95% CI 0.54–0.96). LIMITATIONS, REASONS FOR CAUTION This study is limited by its retrospective design. Furthermore, 56 (16.3%) cases lacked data regarding delivery outcomes, but these were equally distributed between the two groups. WIDER IMPLICATIONS OF THE FINDINGS The lower clinical pregnancy rates per embryo transfer indicate that implantation is hampered after a caesarean section. Its relation with a possible niche (caesarean scar defect) in the uterine caesarean scar needs further study. Our results should be discussed with clinicians and patients who consider an elective caesarean section. STUDY FUNDING/COMPETING INTEREST(S) Not applicable. TRIAL REGISTRATION NUMBER This study has been registered in the Dutch Trial Register (Ref. No. NL7631 http://www.trialregister.nl).

Western and Eastern practices have traditionally differed in their approach to treating lateral lymph nodes in rectal cancer. While Western clinicians have primarily favored neoadjuvant (chemo)radiotherapy to sterilize lateral compartments, Eastern physicians have often opted for the surgical removed of lymphatic tissue with a lateral lymph node dissection without neoadjuvant treatment. The literature suggests similar oncological outcomes for these two separate techniques, while tangible differences exist. The combination of these paradigms may be beneficial in reducing overall morbidity while sustaining low recurrence rates. This article considers traditional Eastern and Western perspectives, discusses nodal features important for predicting malignancy and attempts to stimulate international, multidisciplinary consensus and collaboration.

Objectives In patients with rectal cancer, the size and location of lateral lymph nodes (LLNs) are correlated to increased lateral local recurrence rates. Sufficient knowledge and accuracy when measuring these features are therefore essential. The objective of this study was to evaluate the variation in measurements and anatomical classifications of LLNs before and after training. Methods Fifty-three Dutch radiologists examined three rectal MRI scans and completed a questionnaire. Presence, location, size, and suspiciousness of LLNs were reported. This assessment was repeated after a 2-hour online training by the same radiologists with the same three cases plus three additional cases. Three expert radiologists independently evaluated these 6 cases and served as the standard of reference. Results Correct identification of the anatomical location improved in case 1 (62 to 77% (p = .077)) and in case 2 (46 to 72% (p = .007)) but decreased in case 3 (92 to 74%, p = .453). Compared to the first three cases, cases 4, 5, and 6 all had a higher initial consensus of 73%, 79%, and 85%, respectively. The mean absolute deviation of the short-axis measurements in cases 1–3 were closer—though not significantly—to the expert reference value after training with reduced ranges and standard deviations. Subjective determination of malignancy had a high consensus rate between participants and experts. Conclusion Though finding a high consensus rate for determining malignancy of LLNs, variation in short-axis measurements and anatomical location classifications were present and improved after training. Adequate training would support the challenges involved in evaluating LLNs appropriately. Key Points • Variation was present in the assessment of the anatomical location and short-axis size of lateral lymph nodes. • In certain cases, the accuracy of short-axis measurements and anatomical location, when compared to an expert reference value, improved after a training session. • Consensus before and after training on whether an LLN was subjectively considered to be suspicious for malignancy was high.