Health Services Research / Birth Weight / Pregnancy / Humans / Female / Rio de Janeiro / Young Adult / Newborn Infant / Adult / Maternal Age / Time Factors / Breast feeding / Random-Effects Models / Protective and Risk Factors / Cesarean Section / Public Art Hospitals / Postnatal Care / Prenatal Care / Socioeconomic Factors / Rio de Janeiro / Young Adult / Newborn Infant / Adult / Maternal Age / Time Factors / Breast feeding / Random-Effects Models / Protective and Risk Factors / Cesarean Section / Public Art Hospitals / Postnatal Care / Prenatal Care / Socioeconomic Factors