Objective : During early pregnancy, CD71 and glycophorin A positive cells in peripheral blood of pregnant women were studied, to assess the relationship between increased numbers of nucleated RBC (NRBC) in maternal blood and pregnant outcomes. Methods : Peripheral venous blood samples were obtained from 47 primigravidas of 14∼16 weeks gestation. Triple screening tests were routinely performed. Blood samples were incubated with monoclonal anti-CD71 and monoclonal anti-glycophorin antibodies, and analyzed by flow cytometry using FACSort (Becton Dickinson, USA) for checking the NRBC count. Results : A total of 47 pregnant women were enrolled at 14-16 weeks gestation; one pregnancy had anemia and was excluded from the test, the outcome was unknown for 2 other pregnancies, and twelve pregnancies had 1-4% of NRBC in the maternal blood. In the remaining 32 pregnant women, grouped according to their percentage of NRBC, the group with more than 4% of NRBC was termed the study group, and less than 1% of NRBC was termed the control group. The results were as follows: 1) The study group showed lower fetal birth weight than the control group, which was statistically negatively significant (y=-62.219x + 3,401.6, R2=0.2146, p<0.05). 2) There was no significant correlation between the percentage of NRBC of maternal blood and maternal serum AFP level in the study and the control groups (y=-0.0206x + 1.2763, R2 =0.0096, p>0.05). 3) There were two complications in the study group: one was a preterm delivery at 35 weeks of gestational age with birth weight of 2,300 gm and the other was a case of pregnancy-induced hypertension. Conclusion : It can be concluded that increased NRBC count in maternal blood during the early second trimester has a significant correlation with fetal birth weight but can't predict high risk pregnancies such as preeclampsia, preterm labor or intrauterine fetal growth restriction. In order to obtain a higher predictive value, further studies with more participants and with high risk pregnancies of known risk factors are needed.