The incidence of breast cancer is increasing year by year and the proportion of young patients is also increasing. Because of the youthfulness of breast cancer and the social status of late marriage and childbirth, more young breast cancer patients have an urgent need to have children. Some studies have shown that the pregnancy rate of breast cancer patients after oncology treatment is 40% lower than that of ordinary women of childbearing age. In recent years, domestic and foreign scholars have conducted a lot of research on the safety of reproduction after cancer treatment. The results concluded that ER(+) breast cancer (a subtype of breast cancer) patients who became pregnant within 5 years after breast cancer diagnosis and treatment had comparable disease-free survival in both groups compared to those who did not become pregnant, and pregnancy had no effect on breast cancer recurrence. There is also no increase in the incidence of preterm birth, stillbirth or congenital malformations in fetuses of breast cancer patients. When is the best time to get pregnant? Even though the timing of conception in breast cancer patients is a controversial issue in the oncology industry, a study published in 2017 in the top journal JAMAoncology showed that pregnancy has no negative impact on the survival of breast cancer patients and that for breast cancer patients who wish to become pregnant, pregnancy is safest after 6 months of diagnosis. Most oncologists currently recommend that a comprehensive judgment is needed based on the patient’s level of risk of recurrence, the patient’s wishes, and age at childbirth. (1) For high-risk patients, because of their high risk of recurrence, even if the patient has a strong desire to have children, breast cancer treatment should still be the mainstay in clinical practice. ②For medium and low risk patients, if they have the desire to have children, pregnancy can be considered 2 years after the end of adjuvant therapy, mainly because they want to avoid the window of highest risk of recurrence. ③For patients with hormone receptor positive who need long-term adjuvant endocrine therapy, pregnancy can be discontinued at 2-3 years of endocrine therapy.