We assessed the hematopoietic stem and progenitor (HSPC) cell population in the cord blood of neonates born to mothers with gestational diabetes mellitus (GDM) in a hypothesis generating pilot study, due to that neonatal polycythemia may be the consequence of GDM pregnancy. Forty-five pregnant women with GDM (last trimester mean HbA1C=33.9 mmol/mol) and 42 (non-diabetic) control pregnant women were enrolled after their routine 75g-CH OGTT between the 24-28th gestational week [with expected differences in their mean routine clinical characteristics: plasma glucose at OGTT: 0'=5.07 vs 4.62 mmol/L, 120'=8.9 vs 5.76 mmol/L, age= 35.07 vs 31.66 years, pre-pregnancy BMI=27.9 vs 23.9 kg/m2, GDM vs control respectively] on a voluntary basis after signing the informed consent. EDTA-treated cord blood samples were analyzed by flow cytometry and the software Kaluza1.2 using CD45 and CD34 specific fluorescent antibodies to identify the HSPC cell population (CD34+ cells within the CD45dim blast gate). The proportion of CD34+CD45dim HSPCs among the nucleated cells was significantly (p<0.05, statistical power=60.8%) higher in the cord blood samples of neonates born to mothers with GDM (median: 0.38%) compared to neonates born to non-diabetic mothers (0.32%) and according to treatment types (p<0.05) median: control: 0.32%, GDM-diet only: 0.37%, GDM-on insulin: 0.45%; control vs GDM on insulin (p<0.05). The increased proportion of circulating CD34+CD45dim cells in the cord blood may possibly be related to altered fetal stem cell mobilization in GDM pregnancy, yet these results should be interpreted only as preliminary due to the small sample sizes.