Aim. The aim of the present study was to evaluate the relationship between iron deficiency anemia and small for gestational age (SGA) in early third trimester pregnancies. Methods. A total of 4800 pregnant women who met the inclusion criteria were analyzed retrospectively. We included pregnant women who had iron deficiency anemia between 26(+0) and 30(+0) weeks of gestation and delivered singletons between 37(+0) and 41(+6) weeks of gestation. Patients were divided into four groups according to anemia level: (1) hemoglobin (Hb) < 7 mg/dl (n = 80), (2) Hb 7-9.9 mg/dl (n = 320), (3) Hb 10-10.9 mg/dl (n = 1300), and (4) Hb > 11 mg/dl (n = 3100, control group). The primary outcome of this study was the presence of SGA. Results. The demographic and obstetric characteristics were similar among all the groups. Maternal age, BMI <30 kg/m(2), nulliparity rates, and previous cesarean delivery rates were similar among groups. Ethnicity was significantly different in the severe and moderate anemia groups (<0.001). Mean fetal weight was 2900 +/- 80 g in the severe anemia group, 3050 +/- 100 g in the moderate anemia group, 3350 +/- 310 g in the mild anemia group, and 3400 +/- 310 g in the control group. Fetal weight was significantly lower in the severe and moderate anemia groups compared to the mild anemia and control groups (<0.001). The SGA rate was 18.7% in the severe anemia group, 12.1% in the moderate anemia group, 5.3% in the mild anemia group, and 4.9% in the control group. SGA was significantly higher in the severe and moderate anemia groups compared to the mild anemia and control groups (<0.001). Conclusion. The results of this study indicated that early third trimester severe and moderate iron deficiency anemia was associated with SGA. Iron deficiency anemia in pregnant women may lead to low birth weight.