Gestation and lactation result in metabolic alterations of the dam because of varying demands of the fetus and offspring during the different stages of development. Despite killer whales (Orcinus orca) having one of the longest gestations and highest birth weights of all mammals in human care, these metabolic alterations, and their impact on the physiology of the dam have not been measured. The objectives of this analysis were to determine if physiologic demands on the killer whale during pregnancy and lactation have measurable effects on hematology and biochemical analytes and if detectable, to compare these changes to those which are observed in other mammalian species. Forty hematologic and biochemical analytes from seven female killer whales (22 pregnancies, 1,507 samples) were compared between the following stages: (1) non-pregnant or lactating (control); (2) gestation; and (3) the first 12 months of lactation. Decreased hematocrit, hemoglobin, and red blood cell counts were indicative of plasma volume expansion during mid and late gestation. The killer whales exhibited a progressively increasing physiologic inflammatory state leading up to parturition. Gestation and lactation caused significant shifts in the serum lipid profiles. Gestation and lactation cause significant physiologic changes in the killer whale dam. The last 12 months of gestation had greater physiological impact than lactation, but changes associated with and immediately following parturition were the most dramatic. During this period, killer whales may experience increased susceptibility to illness, and anthropogenic and environmental disturbances.