Introduccion: es importante identificar a las gestantes que tienen riesgo de presentar hipotension arterial postanestesica, cuando son sometidas a cesarea bajo anestesia espinal. Objetivo: identificar si la variabilidad en la presion arterial sistolica (TAS), con los cambios de posicion preoperatoria, es predictor de hipotension arterial postanestesica en cesarea electiva. Metodos: se estudiaron 244 gestantes a termino, programadas para cesarea electivas. Se realizaron mediciones preanestesicas de la TAS en decubito supino y en decubito lateral izquierdo, estimando la diferencia entre las dos mediciones. Se definio hipotension arterial postanestesica, como la TAS menor a 90 mmHg o la caida mayor del 30% de la TAS en supino. Resultados: se presento hipotension arterial postanestesica en 107 (43.8%) de las gestantes. La variacion de la TAS en el grupo que presento hipotension arterial postanestesica fue 10.5 [2.0 a 16.5] vs 2.5 [-6.5 a 6.0] entre las que no la presentaron (P<0,0001). Se estimo que variabilidad mayor a 11 mmHg de la TAS predijo hipotension arterial postanestesica, con sensibilidad: 47.6%, especificidad: 93.4%, LR (+): 7.26, LR (-): 0.58 y area bajo la curva de 0.737 (IC 95%: 0.677-0.791), (p=0.0001). A su vez dicha variacion fue factor de riesgo significativo para la caida de la tension arterial. RR: 2.79 (IC95%: 2.19-3.56). Conclusion: la variacion preanestesica de la TAS, con el cambio de posicion de decubito supino a decubito lateral, fue predictor de hipotension arterial posterior a la colocacion de anestesia espinal en gestantes sometidas a cesarea electivas. Rev.Cienc.Biomed. 2014;5(1):29-34 PALABRAS CLAVE Presion Arterial; Presion Sanguinea; Cesarea; Anestesia Obstetrica. SUMMARY Introduction: It is important to identify to those pregnant women with risk to present postanesthetic arterial hypotension, when they are submitted to cesarean under spinal anesthesia. Objective: to identify if the variability in the systolic arterial pressure (SAP) with the preoperative changes of position is predictor of postanesthetic arterial hypotension in elective cesarean. Methods: 244 women with pregnancy at term, programmed for elective cesarean were studied. Preanesthetic measures of the SAP in supine decubitus and in left lateral decubitus position were carried out, estimating the difference between thetwo measures. Postanesthetic arterial hypotension was defined as SAP lower than 90 mmHg or reduction higher to 30% of the SAP in supine decubitus position . Results: postanesthetic arterial hypotension was presented in 107 (43.8%) of the pregnant women. The variation of the SAP in the group that presented postanesthetic arterial hypotension was 10.5 [2.0 to 16.5] Vs 2.5 [-6.5 to 6.0] between those who did not present it (P<0,0001). It was estimated that variability higher to 11 mmHg of the SAP predicted postanesthetic arterial hypotension with sensibility: 47.6%, specificity: 93.4%, LR (+): 7.26, LR (-): 0.58 and area under the curve of 0.737 (CI 95%: 0.677-0.791), (p=0.0001). In turn such a variation was significant risk factor for the decrease of the arterial pressure. RR: 2.79 (CI95%: 2.19-3.56). Conclusion: the preanesthetic variation of the SAP with the change of position from supine decubitus to lateral decubitus position was predictor of arterial hypotension subsequent to the use of spinal anesthesia in pregnant women submitted to elective cesareans . Rev.Cienc.Biomed. 2014;5(1):29-34 KEYWORDS Arterial Pressure; Blood Pressure; Cesarean Section; Anesthesia, Obstetric.