The study will start at ca. 10h00-12h00 and the women will be fasting since ca. 4 hours. There will be no restriction of water-intake before and throughout the study. An intravenous cannula will be inserted in the antecubital vein of one arm for blood withdrawal. The arm not needed for carrying the baby during breastfeeding will be used (e.g. if the baby is due to drink on the right breast, the intravenous cannula will be put on the left arm, und vice versa). In any case, a support cushion will be used for breastfeeding. The subjects will rest for ca. 30 minutes. Then, a basal blood withdrawal will be performed.