Women where allocated to an oral combined contraceptive pill, or placebo or a LNG-IUS or a etonogestrel-releasing subdermal contraceptive implant at day 42 after delivery. After the provision of the contraceptive method a 0.5 mg/kg of deuterium 99.99% according to the weight of the mother will be administer to all women. One sample of saliva from the mother and the child will be collected every day until 21 days after enrollment. Additionally, weight, height and size of the leg of each child will be measured at baseline, at the day 11 and at the day 21 after enrollment. Also, a diary with information of change of diapers and number of breastfeeding will be kept by each mother.