Breast cancer is currently the most common cancer among Chinese women, with a growth rate more than twice that of the world, and the age of onset is younger, which means that a significant number of patients have not yet had children at the time of diagnosis or still need to have a second child after treatment. So can breast cancer patients have children or not? To give birth or to survive is a tantalizing dilemma! For ethical reasons, clinical trials cannot be conducted on women during pregnancy. But the US NCCN guidelines and the Royal College of Obstetricians and Gynecologists’ Guidelines on Breast Cancer and Pregnancy combine all previous studies to answer some questions about the relationship between fertility and breast cancer. I. Does childbirth increase the rate of recurrence or metastasis of breast cancer? Both guidelines and previous studies conclude that childbirth does not increase the recurrence of breast cancer, does not affect the long-term survival of breast cancer patients, and can even reduce the relative risk of death. However, it is important to consult your doctor and reproductive specialist before pregnancy. Also, there is no significant difference in the incidence of genetic abnormalities and childhood tumors in the offspring born to cancer patients. What should breast cancer patients who have not had children or want to have a second child pay attention to before starting treatment? Chemotherapy and endocrine therapy can damage the ovarian function of women, and some patients may stop menstruation or even lose their fertility after treatment is finished. Therefore, before starting treatment, inform your doctor in charge to choose drugs that have less effect on the ovaries and use ovarian-protective drugs such as gonadotropin-releasing hormone analogs (GnRHa). You can also have your germ cells frozen in advance before chemotherapy to preserve healthy egg cells for artificially assisted techniques. Third, how long after the end of treatment can I have children? Current research shows that it is relatively safe to get pregnant 5 years after surgery. Before pregnancy, do a whole body examination to exclude tumor recurrence and metastasis. Pregnancy is not recommended for metastatic breast cancer that has been diagnosed as advanced. Patients with early stage tumors may also consider pregnancy 2-3 years after surgery. Consider pregnancy after at least 3 months of stopping endocrine drugs (such as tamoxifen). 4. What should I pay attention to during pregnancy and breastfeeding for breast cancer patients? Since chemotherapy and targeted therapy may affect heart function, pregnancy can also increase the cardiopulmonary burden. Echocardiography and other non-radiation methods should be taken seriously during pregnancy. Breastfeeding after breast-conserving surgery is not contraindicated for breast cancer patients after childbirth, but it is not recommended while receiving treatment (e.g. chemotherapy, endocrine therapy). Finally, since there are differences between patients’ conditions, I recommend that before preparing for pregnancy, you must consult a mammographer who understands your condition, and you also need to obtain advice from an obstetrician and fertility doctor.