The authors obtained midline sagittal T1-weighted magnetic resonance images of the pituitary gland in 30 female patients: five pregnant; two postpartum; and 23 nonpregnant, of childbearing age, and without evidence of pituitary gland disorder. In pregnant and postpartum patients, the relative signal intensity of the anterior lobe compared with the pons was statistically higher than that in the control group (P < .001). In the pregnant patients, positive correlation was noted between the signal intensity ratio of the anterior lobe and the pons and gestational age. The authors believe that the hyperintensity of the anterior pituitary lobe in pregnant and postpartum patients is a physiologic variation. Because the anterior lobe of an infant may also be hyperintense on T1-weighted images and because the anterior lobes of an infant and a pregnant woman are histologically similar, the mechanism responsible for the hyperintensity in each case may be the same. It is important to know that the anterior lobe may be hyperintense in pregnant or postpartum women, especially in cases of probable pituitary gland abnormality accompanying pregnancy, such as pituitary hemorrhage, Sheehan syndrome, or lymphocytic adenohypophysitis.