Natural selection associated with birth weight. I. Selection intensity and selective deaths from birth to one month of life.
Differential mortality as a function of birth weight was studied up to the 4th week of life in all single births in Italy in 1974. It was found that: (i) Both selection intensity and selective mortality are much higher with increasing immaturity. (ii) For babies born at term or after 8 months of pregnancy selection intensity tends to relax as early as one week after birth, while for those born after 7 months selection is at work for a longer period. (iii) Selective mortality, on the other hand, keeps increasing after birth but its relevance is relatively decreasing since average mortality after birth continues to decrease.
D001724:Birth Weight; D005260:Female; D005313:Fetal Death; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D011247:Pregnancy; D012641:Selection, Genetic