Fertility capacity has been shown to be one of the main concerns of young cancer survivors. Gonadotoxic treatments may lead to both premature ovarian failure and/or infertility. This review aimed to define which, and when, reproductive indicators should be followed-up to help doctors to counsel patients regarding their fertility and ovarian function, and to determine if a second stage of fertility preservation after the end of cancer treatment is clinically relevant. Longitudinal assessment of anti-Müllerian hormone (AMH) concentrations during cancer treatment indicates the degree of follicular depletion, and allows discrimination between low and high gonadotoxic treatments. Sustained low AMH concentrations after treatment, especially in the case of alkylating protocols, may reduce the duration of the conception window significantly, and expose the patient to the risk of premature ovarian failure. It remains unknown whether this may impact further fertility capacity because of the lack of systematic follow-up of adolescent and young adult (AYA) women after chemo-radiotherapy. It appears that dedicated reproductive follow-up of AYA women under cancer treatment is needed to refine fertility preservation strategies, and to determine if low AMH concentrations after treatment impact the chance of pregnancy in this specific survivor population.