Longitudinal predictions of maternal serum homocysteine, serum B-12, and milk B-12 concentrations according to the presence of depressive symptoms in the 3rd trimester of pregnancy in Rio de Janeiro, Brazil. β Coefficient interactions (βinteraction) and standard error (SE) were estimated. These parameters were used to evaluate the changes of having depressive symptoms on the trajectory of each biological sample. Depressive symptoms were assessed by the Edinburgh Postnatal Depression Scale (EPDS), yes (EPDS ≥11, n = 36) and no (EPDS <11, n = 65). (A) Log serum homocysteine: βinteraction = −0.001 (0.001); p = 0.194, and the model was adjusted for maternal age, education, pre-pregnancy BMI, B-vitamin (including folate) supplement intake during pregnancy, and serum folate concentration at the 3rd trimester of pregnancy. (B) Log serum B-12: βinteraction = −0.001 (0.002); p = 0.445, and the model was adjusted for maternal age, education, pre-pregnancy BMI, B-vitamin (including folate) supplement intake during pregnancy, and serum folate concentration at the 3rd trimester of pregnancy (C) Log milk-B-12: βinteraction = −0.003 (0.004); p = 0.455, and the model was adjusted for pre-pregnancy BMI, B-vitamin (including folate) supplement intake during pregnancy, and serum B-12 concentration at the 3rd trimester of pregnancy. Hcy, homocysteine.