Breast cancer has become the most prevalent malignancy among Chinese women, and the proportion of young patients (less than 40 years old) is close to 20%. With the development of breast cancer treatment, the long-term survival rate of patients is increasing year by year, and the issue of fertility preservation for young breast cancer patients is becoming more and more prominent. Can young breast cancer patients get pregnant? When to get pregnant? How should fertility be preserved? Does pregnancy in breast cancer lead to recurrence Current long-term follow-up studies from multicenter breast cancer patients with pregnancy have shown no adverse effect of pregnancy on disease-free survival and overall survival, regardless of estrogen receptor positivity or negativity. A subgroup analysis of the safety of pregnancy also showed that pregnancy outcome and lactation status had no significant impact on disease-free and overall survival, and that pregnancy is not a contraindication for patients with breast cancer. According to the most recent literature and guidelines, the following fertility protocols are recommended for patients with breast cancer: (1) after surgery and radiation therapy for patients with carcinoma in situ; (2) 2 years after surgery for patients with lymph node negative invasive breast cancer; (3) 5 years after surgery for patients with lymph node positive invasive breast cancer; (4) for patients requiring adjuvant endocrine therapy, discontinue endocrine therapy 3 months prior to conception and continue until lactation is completed. (4) For patients requiring adjuvant endocrine therapy, endocrine therapy should be discontinued 3 months prior to conception until the end of breastfeeding after childbirth and then continued. Fertility preservation methods: Fertility preservation techniques are gradually being developed and many methods are available to preserve ovarian function in young breast cancer patients, including in vitro cryopreservation techniques and/or protective treatment with GnRH agonists. However, these methods have their own advantages and disadvantages. Egg freezing and embryo freezing: Among fertility preservation techniques, the more established ones used are embryo freezing and mature oocyte freezing. Egg freezing or embryo freezing needs to be performed in an experienced fertility center with ovulation in order to obtain a sufficient number of eggs. Ovulation in breast cancer patients can be performed with antagonists or microstimulation protocols, and the use or addition of AI drugs can avoid the proliferation of breast cancer cells due to excessive estrogen levels during ovarian stimulation. Ovarian tissue freezing: Ovarian tissue freezing preserves not only the germ cells but also the ovarian tissue that restores reproductive endocrine production, and is the only in vitro fertility preservation strategy available for prepubertal women, as well as for women who have already started chemotherapy (within 1 to 2 cycles). This option is suitable for patients who require chemotherapy, have a low risk of metastasis of cancerous ovarian tissue, and has good applicability in breast cancer patients because it does not require the use of ovulation-promoting drugs. However, patients with BRCA1/2 germline gene mutations are at risk for ovarian tissue freezing for migration back due to the presence of ovarian cancer susceptibility. GnRH for ovarian protection: Currently, there is no uniform conclusion on the effectiveness of the GnRH regimen when applied for fertility preservation. However, given the ease of clinical use of GnRH in combination with chemotherapy, the lack of impact on the efficacy of chemotherapy, and the potential to reduce ovarian damage caused by chemotherapy, it is recommended as an option for women with all breast cancer strains requiring chemotherapy who wish to preserve fertility and/or ovarian function, and can be used in conjunction with other fertility preservation modalities. Fertility preservation can be used in conjunction with other fertility preservation modalities. Timing of Fertility Preservation Interventions The best time to intervene for fertility preservation is to ask the patient about her wishes and to begin preparations for fertility preservation prior to cancer treatment. In many cases, however, the patient may have already received part of her treatment (surgery, chemotherapy, etc.), but this should not be a contraindication for the patient to undergo fertility preservation counseling.