On the basis of inclusion and exclusion criteria, we will selected 40 puerperae aged 18 to 35 years at the Low Risk Prenatal Care Program of the University Hospital of Ribeirão Preto, University of São Paulo (HC-FMRP). The subjects will be randomized to two types of treatment (etonogestrel-releasing implant to be inserted 24 to 48 hours after delivery or 150 mg medroxyprogesterone administered every three months starting 6 weeks after delivery). Blood samples (40 mL) will be collected in a single procedure from these patients and stored for later determination of multiple hemostatic and metabolic variables at 24-48 hours and at 6 and 12 weeks after delivery. Data on maternal and neonatal clinical parameter will be also collected.