RESUMEN
To analyze and compare the Ground Reaction Forces 9GRF), during the stance phase of walking in pregnant women in the 3rd trimester of pregnancy, and no pregnant women. Methods: 20 women, 10 pregnant and 10 non pregnant, voluntarily took part in this study.: GRF were measured (1000Hz) using a force platform (BERTEC 4060-15), an amplifier (BERTEC AM 6300) and an analogical-digital converter of 16 Bits (Biopac). Results: The study showed that there were significant differences among the two groups concerning absolute values the most significant differences were verified in the maximuns values of vertical force (Fz3,Fz1) and in the impulse of the antero-posterior force (Fy2), taxes of growth of the vertical force, and in the period of time for the antero-posterior force 9Fy) be null. Conclusions: It is easier for the pregnant to continue foeward movement (push-off phase). O smaller growth rates in what concerns to the maximum of the vertical force (Fz1) for the pregnant, can be associated with a slower speed of gait, as an adaptation stretegy to maintain the balance, to compensate the alterations in the position of ther center of gravity due to the load increase. The date related to the antrero-posterior component of the force (Fy), shows that there is a significant difference between the pregnant woman's left foot, which accuses a different functional behavior in each one of the feet, during the propulsion phase.