پیامد تکاملی شیرخواران نارس و کم وزن

Fetal and extrauterine life form a continuum during which human growth and development are affected by genetic، environmental، and social factors. Perinatal mortality is influenced by prenatal، maternal، and fetal conditions and by circumstances surrounding delivery. The majority of infants'' deaths and developmental disorders are due to disorders relating to prematurity and unspecified low birth weight (LBW)، as well as maternal complications of pregnancy and congenital malformations (chromosomal and metabolic). Birth weight less than 2500 g (as result of preterm delivery and/or intra uterine growth restriction) is a major cause of both neonatal and infant mortality rates and، together with congenital anomalies (eg. cardiac، central nervous، and respiratory system)، contributes significantly to childhood morbidity. Low birth weight is caused by preterm birth، intrauterine growth retardation (IUGR)، or both factors. The predominant cause of LBW in developed countries is preterm birth، whereas in developing countries، the cause is more often IUGR. Although IUGR does not appear to further increase the risk of mortality in preterm infants، both morbidity and mortality are increased in term growth-restricted infants. Infants weghing less than 1500 g are most often premature (<37 weeks of gestation)، although IUGR may also complicate the early delivery. Eventhough very low birth weight occurs in only 1-2% of all infants، these births represent a large proportion of the neonatal and infant mortality and infants with both short- and long-term complications، including neurodevelopmental handicaps. At school age، VLBW infants have poorer physical growth، cognitive function، and school performance. These disadvantages appear to persist into adulthood and therefore have broad implications for society. A number of well-designed clinical research studies have demonstrated a powerful interaction between biological and environmental risk and protective factors within the infant and the environment.