STUDY THE EFFECTS OF EARLY BREASTFEEDING AND FACTORS RELATED TO UTERINE INVOLUTION POSTPARTUM IN PRIMIPAROUS, NATURAL BIRTH AT OBSTETRICS DEPARTMENT - BACH MAI HOSPITAL Objective research study for the effects of early breastfeeding infants up uterine involution in postpartum women often at Bach Mai Hospital Obstetrics and described several factors affecting woman's uterus in postpartum Subjects and Methods: A prospective study, cross-sectional descriptive comparison group to assess uterine involution and factors affecting involution uterus.