Cases were defined as patients with diagnosis of preeclampsia (pregnancy-induced hypertension (≥140/90 mm Hg of blood pressure with significant proteinuria (≥300 mg/24 h). Controls were defined as patients with term pregnancy through vaginal or cesarean delivery, without pathology or with pathology different from the case, with adherence to prenatal control. For each case identified during each month, three controls were chosen through random sampling.