FACTORS INFLUENCING HUMAN BIRTH-WEIGHT IN NORMAL-PREGNANCY - A PROSPECTIVE-STUDY IN A BRAZILIAN UNIVERSITY HOSPITAL

The effects of 17 variables on birth weight have been assessed in a pr ospective study of 1,045 singletons without major malformations, born at a Brazilian teaching hospital to mothers with neither diabetes mell itus nor chronic hypertension. These variables were as follows: sex of the newborn, gestational age at delivery, type of delivery, birth ord er of the newborn, placental shape, placental weight, umbilical cord l ength, point of insertion of the umbilical cord in the placenta, consa nguinity between the parents of the newborn, meternal skin color, heig ht and age, paternal age, trimesters of antenatal care, average number of cigarettes smoked daily during pregnancy, meternal schooling, and economic status of the newborn's family. The interrelations between th ese variables were analysed in order to investigate their relative imp ortance as determinants of birth weight variations. Only gestational a ge, placental weight, smoking during pregnancy, maternal height, sex o f the newborn and birth order were retained as significant factors, in fluencing and explaining 60% of the total variance of birth weight. Am ong these factors, gestational age and placental weight were the most important since they explained 40% and 16%, respectively of the total variance of birth weight.