We studied the effects of corn oil and perilla oil intake by rats during pregnancy and lactation on the composition of the stomach contents and plasma lipids concentration in their pups. Two groups of dams were fed either a corn oil diet (CD) or a perilla oil diet (PD) during their pregnancy and lactation. On days 8, 21 and 33 after birth, two pups each from the litters of all dams were killed and their blood and stomach were collected. A long chain polyunsaturated fatty acid (LCPUFA; C_20-22) not presented in the dams diet was detected in the stomach breast milk of both groups. Although the n-3 fatty acids of LCPUFA in the stomach of the PD group was higher than that of the CD group, no significant difference in the arachidonic acid (AA; 20:4) and docosahexaenoic acid (DHA; 22:6) was observed between the two groups. The plasma lipid concentration in the pups of the PD group was lower than that of the CD group, but there was no significant difference in the two groups after weaning. Therefore, α-lindenic acid (ALA; 18:3) in the PD was synthesized into eicosapentaenoic acid (EPA; 20:5) and DHA in the dam's body and added to the breast milk, which indicated that the plasma lipids concentration in the pups nursed by the dams fed the PD decreased during lactation.