The American Society of Breast Surgeons (ASBrS), American College of Radiology (ACR), and Society of Breast Imaging (SBI) recommend screening mammograms yearly beginning at the age of 40, including during pregnancy and lactation. Mammograms, ultrasounds, and MRI’s are safe during breastfeeding.
Similarly, the American College of Obstetrics and Gynecologists has a statement discussing safety of MRI and CT scan with contrast during pregnancy if one of those studies is needed and other publications corroborate this.
Via early detection, mammograms improve survival from breast cancer. I describe these recommendations in a blog post for the United States Lactation Consultant Association.
Mammograms are safe and effective. Radiation incurred with a mammogram is 3-5 mGray, equivalent to backgrounds levels incurred over two months or taking a plane flight.