The aim of the study was to evaluate predictors of disease flares during pregnancy and obstetric and fetal complications in a cohort of systemic lupus erythematosus (SLE) patients. One hundred and thirty-two pregnancies in 96 SLE patients were prospectively followed by monthly clinical and laboratory evaluations. Predictors of lupus flares, fetal and obstetric complications during pregnancy were identified performing stepwise logistic regression analysis. Maternal lupus flares occurred in 57 % of pregnancies and were being best predicted by the number of flares before conception. Manifestations during flares were best predicted by the same features occurred before conception: dermatological flares by skin rash, renal flares by nephritis, and hematological flares by hematological abnormalities. There were 110 live births and 22 fetal losses. Among live newborns, 22 % were premature. Fetal loss was best predicted by hypertension at conception; miscarriages by the amount of steroids taken during the last year before conception; stillbirth by the number of flares during the last year before conception; preterm birth by the coexistence of anti-phospholipid antibody syndrome and anti-double-stranded DNA antibody levels before conception; premature rupture of membranes by high ECLAM score during the 6 months before conception, small for gestation age by hypertension at conception; and preeclampsia by positive lupus anticoagulant. Some independent predictors of lupus flares and fetal and obstetric complications were identified, which can help the risk assessment of pregnancy in SLE patients.