There have been numerous studies that have attempted, with varying degrees of success, to show links between birth weight and later-life conditions, including diabetes, obesity, tobacco smoking and intelligence.
There are basically two distinct determinants for birth weight:
- The duration of gestation prior to birth, that is, the gestational age at which the child is born
- The prenatal growth rate, generally measured in relation to what weight is expected for any gestational age.
The incidence of birth weight being outside what is normal is influenced by the parents in numerous ways, including:
- The health of the mother, particularly during the pregnancy
- Environmental factors, including exposure of the mother to secondhand smoke
- Economic status of the parents gives inconsistent study findings according to a review on 2010, and remains speculative as a determinant.
- Other factors, like multiple births, where each baby is likely to be outside the AGA, one more so than the other
- A low birth weight can be caused either by a preterm birth (low gestational age at birth) or of the infant being small for gestational age (slow prenatal growth rate), or a combination of both.
- A very large birth weight is usually caused by the infant having been large for gestational age
Influence on adult life 
A baby born small or large for gestational age (either of the two extremes) is thought to have an increased risk of obesity in later life, but it was also shown that this relationship is fully explained by maternal weight.
GH therapy at a certain dose induced catch-up of lean body mass (LBM). However percentage body fat decreased in the GH-treated subjects. Bone mineral density SDS measured by DEXA increased significantly in the GH-treated group compared to the untreated subjects, though there is much debate over whether or not SGA (small for gestational age) is significantly adverse to children to warrant inducing catch-up.
See also 
- Definitions from Georgia Department of Public Health. Date: 12/04/2008. Original citation: "Birthweight: Infant's weight recorded at the time of birth"
- "The Health Consequences of Involuntary Exposure to Tobacco Smoke: A Report of the Surgeon General". Surgeon General of the United States. 2006-06-27. Retrieved 2009-02-07. pp. 198–205
- Margerison Zilko CE (January 2010). "Economic contraction and birth outcomes: an integrative review". Hum Reprod Update 16 (4): 445–458. doi:10.1093/humupd/dmp059. PMID 20085917.
- "3 stages of childhood may predict obesity risk - Fitness - MSNBC.com". Retrieved 2007-11-28.
- Singhal A, Wells J, Cole TJ, Fewtrell M, Lucas A (1 March 2003). "Programming of lean body mass: a link between birth weight, obesity, and cardiovascular disease?". Am J Clin Nutr. 77 (3): 726–30. PMID 12600868.
- Parsons TJ, Power C, Manor O (December 2001). "Fetal and early life growth and body mass index from birth to early adulthood in 1958 British cohort: longitudinal study". BMJ 323 (7325): 1331–5. doi:10.1136/bmj.323.7325.1331. PMC 60670. PMID 11739217.
- "GH Treatment Effects on Body Composition in SGA". Growth, Genetics & Hormones 24 (1). May 2008.
- "Low birth weight diabetes link". BBC News. 2005-02-25. Retrieved 2007-11-28.
- Gillman MW, Rifas-Shiman S, Berkey CS, Field AE, Colditz GA (March 2003). "Maternal gestational diabetes, birth weight, and adolescent obesity". Pediatrics 111 (3): e221–6. doi:10.1542/peds.111.3.e221. PMID 12612275.
- Rich-Edwards JW, Colditz GA, Stampfer MJ et al. (1999). "Birthweight and the risk for type 2 diabetes mellitus in adult women". Ann Intern Med. 130 (4 Pt 1): 278–84. PMID 10068385.
- Matte TD, Bresnahan M, Begg MD, Susser E (August 2001). "Influence of variation in birth weight within normal range and within sibships on IQ at age 7 years: cohort study". BMJ 323 (7308): 310–4. doi:10.1136/bmj.323.7308.310. PMC 37317. PMID 11498487.
- "The Future of Children - Sub-Sections". Archived from the original on 2007-10-22. Retrieved 2007-11-28.
- "HEALTH | Intelligence linked to birthweight". BBC News. 2001-08-09. Retrieved 2007-11-28.
- "Mortality and Burden of Disease Estimates for WHO Member States in 2002" (xls). World Health Organization. 2002.
- MedlinePlus Encyclopedia Intrauterine growth restriction
- Peleg D, Kennedy CM, Hunter SK (August 1998). "Intrauterine growth restriction: identification and management". Am Fam Physician 58 (2): 453–60, 466–7. PMID 9713399.
- "Intrauterine growth restriction (IUGR)" at Health System, University of Virginia
- Fetal Growth Restriction at eMedicine
- "Researchers link low birth weight to lower achievement"
- "Management of Suspected Fetal Macrosomia"
- "Vit D linked to baby birth weight" at BBC News, 25 April 2006
- Born in Bradford - 2006 cohort study into the causes of low birth weight and infant mortality in Bradford, UK
- Intrauterine Growth Restriction Help - IUGR factors and solutions
- Walid MS, Astafyeva OV, Pomortsev AV (December 2007). "The IUGR prognostic scale". Arch Gynecol Obstet. 276 (6): 633–40. doi:10.1007/s00404-007-0398-1. PMID 17619893.