OBJECTIVE We aimed to determine the association of villitis of unknown etiology (VUE) in complicated and uncomplicated pregnancies. METHODS Placentas from term pregnancies (≥37 weeks) were sent to histopathology evaluation. Maternal and labor characteristics and pathological reports were compared between placentas with VUE (VUE group) and without VUE (controls). Immunohistochemical studies were performed to identify T-cells infiltration in foci of VUE. Placentas were analyzed for concomitant lesions consistent with maternal malperfusion, fetal vascular supply and inflammatory lesions. Small for gestational age (SGA) was defined as birth weight below the 10th %. RESULTS A total of 1203 placentas were obtained, in which VUE was diagnosed in 5% (n = 60). Compared to controls ((n = 1143), the VUE group was characterized by lower birth weights, p < 0.001, higher rate of SGA, p = 0.009 and lower placental weight, p < 0.001. By logistic regression analysis, after controlling for gestational age, nulliparity, pregnancy complications, obesity, smoking and SGA, only SGA was found to be independently associated with VUE, aOR: 2.3, 95% CI: 1.2-4.4, p = 0.012. Additionally, VUA and maternal malperfusion lesions were found to be independent risk factors for the development SGA. CONCLUSIONS VUE is associated with lower birth weights, SGA and lower placental weight. Both VUE and maternal malperfusion lesions are risk factors for the development of SGA.