PURPOSE: Sentinel lymph node biopsy (SLNB) is currently not recommended in pregnant patients with breast cancer due to radiation concerns. METHODS: Twelve pregnant patients with breast cancer received low-dose (10 MBq on average) lymphoscintigraphy using (99m)Tc human serum albumin nanocolloids. RESULTS: The sentinel lymph node (SLN) was identified in all patients. Of the 12 patients, 10 had pathologically negative SLN. One patient had micrometastasis in one of four SLN. One patient had metastasis in the SLN and underwent axillary clearance. From the 12 pregnancies, 11 healthy babies were born with no malformations and normal weight. One baby, whose mother underwent lymphatic mapping during the 26th week of gestation, was operated on at the age of 3 months for a ventricular septal defect and at 43 months was in good health. This malformation was suspected at the morphological US examination during week 21, well before lymphoscintigraphy, and was confirmed a posteriori by a different observer based on videotaped material. No overt axillary recurrence appeared in the patients with negative SLNs after a median follow-up of 32 months. CONCLUSION: Our experience supports the safety of SLNB in pregnant patients with breast cancer, when performed with a low-dose lymphoscintigraphic technique.