Low birth weight has been a mystery for science throughout the ages. Many investigations have been carried out on the causes that produce it and the consequences it provokes. Birth weight is one of the variables recognized as one of the most important because of its association with increased risk of mortality in any period, especially in the perinatal period. Birth weight is undoubtedly the most important determinant of a newborn's chances of experiencing satisfactory growth and development. For this reason, the rate of low birth weight newborns is currently considered as a general health indicator, since it has a multifactorial cause that is due to maternal problems as well as fetal and environmental problems.