Purpose: To evaluate the levels of peripheral blood CD34+ cells in women who subsequently had a spontaneous miscarriage (SM).Materials and Methods: We enrolled 11 women who had SM, matching them for age, BMI and gestational age with 33 healthy pregnancies (controls). From a blood sample at 9th-11th weeks of pregnancy, we evaluated PAPP-A, free β-hCG, T (suppressor and helper), NK, B, CD34+ cells.Results: In peripheral blood of women who had SM, PAPP-A and CD34+ cells were significantly lower (p < 0.001) compared to control group.Conclusions: CD34+ cell low level in peripheral blood is associated with increased risk of SM. [ABSTRACT FROM AUTHOR]