The fetal middle cerebral artery-peak systolic velocity (MCA-PSV) is a noninvasive tool for detection of intrauterine fetal anemia. Premature restriction of foramen ovale (FO) may prevent proper blood supply to the fetal brain. We presented a 29-year-old Rhesus-negative mother who had been referred to our center due to positive indirect Coombs test. A single live intrauterine fetus at 30 weeks of gestation was observed with normal MCA-PSV- multiples of the median (MoM). The mother was under weekly follow up due to an isoimmunized pregnancy. In the third week of follow-up, the MCA-PSV- MoM was within the normal range though fetal echocardiography showed that the findings were in favor of premature restriction of FO; so premature delivery was decided at the same day. A boy was delivered with significant paleness, hemoglobin level of 3 g/dL, positive direct Coombs test, and reticulocyte count of 20%. These findings resulted in a significant intrauterine hemolysis process due to Rh alloimmunization not detected by Doppler examination of MCA- PSV during pregnancy. The aim of this study was to show that MCA-PSV- MoM may not be a diagnostic method for detection of possible anemia in the fetus with congenital heart disease.