Although up to 50% of pregnant women suffer from back pain, the cause of this pain is unknown. As part of a larger study on back pain and work during pregnancy, the task of lifting a file folder from a low drawer was selected for biomechanical analysis. Six pregnant subjects and six non-pregnant control subjects were recruited to participate in the task analysis. Each pregnant subject was asked to attend a minimum of 2 visits at either 20 and 34 weeks of pregnancy, or, 34 weeks and 2 months postpartum. Nonpregnant subjects, matched for height and pre-pregnancy weight with the pregnant subjects each attended two lifting sessions in order to obtain a measure of the expected trial-to-trial variation of the testing parameters. The position and orientation of individual body segments throughout the course of the lifting task were monitored using a six degree-of-freedom tracking system (MotionStar®). Individualized anthropometric data were collected using Jensen’s Elliptical Cylinder model. A 3-D, dynamic, hands-down link segment model was used to determine the loading at L5/S1 during the lifting task. In addition to kinetic parameters, changes in posture and lifting style as a result of the stage of pregnancy were also examined by calculation of the relative angles between the magnetic sensors on each of the body segments of interest. In general, forces and moments at L5/S1 were found to be greater in late pregnancy than in early pregnancy and for the non-pregnant group. Peak forces for the postpartum trials were lower than those in late pregnancy, however, moments at L5/S1 were higher postpartum. In general, postpartum subjects used a greater peak range of motion during the lifting trials.