The PREgnancy and FERtility (PREFER) study is a comprehensive program aiming to optimize care and improve knowledge around the topics of fertility preservation and pregnancy issues in young breast cancer patients. The program was initiated at the National Institute for Cancer Research, IRCCS AOU San Martino - IST in Genova (Liguria Region, Italy) and then it has been spread to other Italian Institutions under the umbrella of the Gruppo Italiano Mammella (GIM) study group. It is composed of two distinctive studies, one assessing fertility (i.e. PREFER-FERTILITY) and the other pregnancy (PREFER-PREGNANCY) issues. Hence, two different study protocols were developed under the umbrella of the PREFER registry. PREFER-FERTILITY aims to obtain and centralize data about the preferences and choices of young cancer patients on the fertility preservation strategies available in Italy. Furthermore, it aims to assess the outcomes of patients undergoing one or more strategies for fertility preservation in terms of success of the techniques (i.e. recovery of ovarian function, number of cryopreserved oocytes, post-treatment pregnancies) and safety (i.e. long-term survival outcomes). PREFER-PREGNANCY has two main objectives: 1) to obtain and centralize data on the management of breast cancer diagnosed during pregnancy, the obstetrical and paediatric care of children born after prior in utero exposure to anticancer treatments, and the long-term survival outcomes of these patients; 2) to obtain and centralize data on the clinical outcomes of breast cancer survivors that achieve a pregnancy after prior diagnosis and treatment of breast cancer.