The aim of our study was to evaluate the immediate changes on the fetal heart rate (FHR) and the fetal umbilical artery pulsatility index (UPI) after performing genetic amniocentesis. This was a prospective study including 431 consecutive singleton pregnancies between 14 and 18 weeks undergoing genetic amniocentesis in our institution. Doppler measurements were obtained transabdominally before and immediately after the procedure. Structural malformations detected by ultrasound were excluded. Student's t-test was performed for comparisons among different groups and observed mean changes. The results showed a significant decrease in FHR post-amniocentesis (mean 1.5 beats, t = 3.47, P < 0.01) and a non-significant elevation in UPI (mean -0.01, t = -0.29, P = 0.77) after the procedure. Differences in FHR could be found when analyzed by each gestational week. These preliminary data suggest that although acute fetal hemodynamic changes are detected after genetic amniocentesis, such changes are unlikely to have clinical relevance. However, it is reasonable to propose the use of Doppler as a method of assessing hemodynamic effects caused by prenatal invasive procedures in order to provide more accurate in vivo research on this issue.