A noninvasive hemodynamic study in three moments of the gamete intrafallopian transfer (GIFT) cycle was carried out on 25 patients: before beginning multiple follicular stimulation (MFS) (study I); after rapid increase of serum estradiol (E2) (study II); and 12 days after GIFT (study III). In the 25 patients, the rapid increase in E2 proved to be combined with a significant increase in the left ventricular end diastolic dimension (LVEDD), the left ventricular end systolic dimension, the heart rate (HR), the systolic index, the cardiac index, and a significant reduction in the mean arterial pressure, in the systolic arterial pressure and in the systemic vascular resistence index. In the 14 pregnant patients in study III, all of the hemodynamic parameters studied proved to be significantly modified with respect to study I. In the 11 nonpregnant patients between Studies I and III were no significant cardiovascular modifications except for a significant increase in LVEDD in Study III. It is concluded that, during MFS, the rapid increase in E2 is combined with hemodynamic modifications and that, in pregnancy, the cardiovascular adaptation modifications occur in the very early stages.