Breast cancer during pregnancy (BCP), although rare, is becoming more common and treatment should be as similar as possible to that for nonpregnant young patients with breast cancer. A group of specialists convened to review current guidelines and provide guidance on how recent advances in breast cancer diagnosis and treatment can be adapted for pregnant patients. The majority of patients with BCP will be considered for treatment during the pregnancy. Premature delivery should be avoided whenever possible. Most treatments, including sentinel lymph node biopsy, systemic therapy with taxanes, platinum agents, or dose-dense treatment can be safely given during pregnancy, after careful risk/benefit assessment for mother and child. Chemotherapy is contraindicated during the first trimester because of a higher risk of fetal malformations but is feasible in the second and third trimesters. Other treatments such as radiation therapy or anti-human epidermal growth receptor 2 treatment are in general not indicated during pregnancy but might be considered in some instances. Patient data should be collected in a systematic way whenever possible.