BACKGROUND Endometrial cancer is common and usually occurs after menopause, but the number of women diagnosed during reproductive age is increasing. The standard treatment including hysterectomy is effective but causes absolute uterine factor infertility. In order to avoid or postpone surgery, conservative management of endometrial cancer (CMEC) has been proposed for younger women who want to retain their fertility. OBJECTIVE AND RATIONALE The main objective of this study was to estimate the chances of pregnancy and live birth for women with early-stage endometrial cancer (EEC) who are managed conservatively for fertility preservation. SEARCH METHODS The PRISMA recommendations for systematic reviews and meta-analyses were followed. Structured searches were performed in PubMed, Embase and the Cochrane Library, from inception until 13 June 2021. Inclusion was based on the following criteria: group or subgroup of women with Clinical Stage IA, well-differentiated, endometrioid endometrial cancer (from now on, EEC); CMEC for fertility preservation; and reported frequencies of women achieving pregnancy and/or live birth after CMEC. The following exclusion criteria applied: impossibility to isolate/extract outcome data of interest; second-line CMEC for persistent/recurrent disease; CMEC in the presence of synchronous tumours; case reports; non-original or duplicated data; and articles not in English. Qualitative synthesis was performed by means of tabulation and narrative review of the study characteristics. Study quality was assessed with an ad hoc instrument and several moderator and sensitivity analyses were performed. OUTCOMES Out of 1275 unique records, 133 were assessed in full-text and 46 studies were included in the review. Data from 861 women with EEC undergoing CMEC were available. Progestin-based treatment was reported in all but three studies (93.5%; 836 women). Complete response to treatment was achieved in 79.7% of women, with 35.3% of them having a disease recurrence during follow-up. Of 286 pregnancies obtained after CMEC; 69.4% led to live birth (9% of them multiple births) and 66.7% were achieved through fertility treatment. Based on random-effects meta-analyses, women treated with progestin-based CMEC have a 26.7% chance of achieving pregnancy (95% CI 21.3–32.3; I2 = 53.7%; 42 studies, 826 women) and a 20.5% chance to achieve a live birth (95% CI 15.7–25.8; I2 = 40.2%; 39 studies, 650 women). Sample size, average age, publication year, study design and quality score were not associated with the outcomes of progestin-based CMEC in moderator analyses with meta-regression. However, mean follow-up length (in months) was positively associated with the chances of pregnancy (regression coefficient [B] = 0.003; 95% CI 0.001–0.005; P = 0.006) and live birth (B = 0.005; 95% CI 0.003–0.007; P < 0.001). In sensitivity analyses, the highest chances of live birth were estimated in subsets of studies including only women of age 35 or younger (30.7%), the combination of progestins with hysteroscopic resection (30.7%), or at least 3 years of follow-up (42.4%). WIDER IMPLICATIONS Progestin-based CMEC is viable for women with well-differentiated, Clinical Stage 1A, endometrioid endometrial cancer who want to preserve their fertility, but there is room for improvement as only one-fifth of them are estimated to achieve live birth according to this meta-analysis. Further investigations on prognosis-driven selection, hysteroscopic resection and long-term surveillance are arguably needed to improve the reproductive outcomes of CMEC.