Small for gestational age

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Small for gestational age
Weight vs gestational Age.jpg
Graph showing which babies fit the definition of small. (DiseaseDB #31952)
Specialty Pediatrics   OOjs UI icon edit-ltr-progressive.svg

Small for gestational age (SGA) newborns are those who are smaller in size than normal for the gestational age. SGA is most commonly defined as a weight below the 10th percentile for the gestational age. [1] SGA predicts susceptibility to hypoglycemia, hypothermia, and polycythemia. [2] By definition, at least 10% of all newborns will be labeled SGA. All SGA babies should be watched for signs of failure to thrive, hypoglycemia, and other health conditions.

Contents

Causes

Being small for gestational age is broadly either: [3]

Diagnosis

The condition is defined by birth weight and/or length.[ citation needed ]

Intrauterine growth restriction is generally diagnosed by measuring the mother's uterus, with the fundal height being less than it should be for that stage of the pregnancy. If it is suspected, the mother will usually be sent for an ultrasound to confirm.[ citation needed ]

Management

Ninety percent of babies born SGA catch up in growth by the time they reach two years old. For the ten percent of those without catch-up growth by two years old, an endocrinologist should be consulted. Some cases warrant growth hormone therapy.[ citation needed ]

Hypoglycemia is common in asymmetrical SGA babies because their larger brains burn calories at a faster rate than their usually limited fat stores can hold. Hypoglycemia is treated by frequent feedings and/or additions of cornstarch-based products (such as Duocal powder) to the feedings.[ citation needed ]

Some common conditions and disorders are found in many babies who are SGA (and especially those without catch-up growth by two years old).[ citation needed ]

For intrauterine growth restriction (during pregnancy), possible treatments include the early induction of labor, though this is only done if the condition has been diagnosed and seen as a risk to the health of the fetus.[ citation needed ]

Terminology

If small for gestational age babies have been the subject of intrauterine growth restriction, formerly known as intrauterine growth retardation, [5] the term "SGA associated with intrauterine growth restriction" is used. Intrauterine growth restriction refers to a condition in which a fetus is unable to achieve its genetically determined potential size. This functional definition seeks to identify a population of fetuses at risk for modifiable but otherwise poor outcomes. This definition intentionally excludes fetuses that are small for gestational age (SGA) but are not pathologically small. [3] Infants born SGA with severe short stature (or severe SGA) are defined as having a length less than 2.5 standard deviation scores below the mean. [6]

A related term is low birth weight, defined as an infant with a birth weight (that is, mass at the time of birth [7] ) of less than 2,500 g (5 lb 8 oz), regardless of gestational age at the time of birth. Other related terms include "very low birth weight", which is less than 1,500 g (3 lb 5 oz); and "extremely low birth weight", which is less than 1,000 g (2 lb 3 oz). [8] Normal weight at term delivery is 2,500–4,200 g (5 lb 8 oz – 9 lb 4 oz).[ citation needed ]

SGA is not a synonym of low birth weight, very low birth weight, or extremely low birth weight. For example, with a 35-week gestational age delivery, a weight of 2,250 g (4 lb 15 oz) is appropriate for gestational age but is still low birth weight. One third of low-birth-weight neonates – infants weighing less than 2,500 g (5 lb 8 oz) – are small for gestational age.[ citation needed ]

There is an 8.1% incidence of low birth weight in developed countries and 6–30% in developing countries. Much of this can be attributed to the health of the mother during pregnancy. One-third of babies born with a low birth weight are also small for gestational age. Infants that are born at low birth weights are at risk of developing neonatal infection.[ citation needed ]

Both low and high maternal serum Vitamin D (25-OH) are associated with higher incidence SGA in white women, although the correlation does not seem to hold for African American women. [9]

Mean weight for gestational age at birth with standard deviation and 10th percentile calculated by Z-score [10]
Gestational age at birth (weeks)Mean weight (grams)SD10th%
2246792354
23553109416
24626129473
25714156529
26819186597
27935215677
281073242770
291211269882
3013963091018
3115883361166
3218003711335
3320334051538
3422964281772
3525604402021
3627994412261
3730284562477
3832094322665
3933334192810
4034174162904
4134864222958
4235124292985
4335504442981
4435055032952

References

  1. Small for gestational age (SGA) at MedlinePlus. Update Date: 8/4/2009. Updated by: Linda J. Vorvick. Also reviewed by David Zieve.
  2. Cunningham, F. Gary; Leveno, Kenneth J.; Bloom, Steven L.; Spong, Catherine Y.; Dashe, Jodi S.; Hoffman, Barbara L.; Casey, Brian M.; Sheffield, Jeanne S. (2013). Williams Obstetrics (24 ed.). New York, NY: McGraw-Hill Education.
  3. 1 2 Ross, Michael G. "eMedicine - Fetal Growth Restriction" . Retrieved 2010-02-25.
  4. Barker, D. J. P., ed. (1992). Fetal and infant origins of adult disease. London: British Medical Journal. ISBN   0-7279-0743-3.
  5. Dogra, Vikram S. "eMedicine - Intrauterine Growth Retardation" . Retrieved 2007-11-28.
  6. Clayton, PE; Cianfarani, S; Czernichow, P; Johannsson, G; Rapaport, R; Rogol, A (March 2007). "Management of the child born small for gestational age through to adulthood: a consensus statement of the International Societies of Pediatric Endocrinology and the Growth Hormone Research Society". The Journal of Clinical Endocrinology and Metabolism. 92 (3): 804–10. doi: 10.1210/jc.2006-2017 . hdl: 2108/45969 . PMID   17200164.
  7. Definitions Archived 2012-04-02 at the Wayback Machine from Georgia Department of Public Health. Date: 12/04/2008. Original citation: "Birthweight: Infant's weight recorded at the time of birth"
  8. Subramanian, KN Siva. "eMedicine - Extremely Low Birth Weight Infant" . Retrieved 2007-11-28.
  9. Bodnar, LM; Catov, JM; Zmuda, JM; Cooper, ME; Parrott, MS; Roberts, JM; Marazita, ML; Simhan, HN (May 2010). "Maternal serum 25-hydroxyvitamin D concentrations are associated with small-for-gestational-age births in white women". Journal of Nutrition. 140 (5): 999–1006. doi:10.3945/jn.109.119636. PMC   2855265 . PMID   20200114.
  10. Talge, Nicole M.; Mudd, Lanay M.; Sikorskii, Alla; Basso, Olga (2014-05-01). "United States Birth Weight Reference Corrected For Implausible Gestational Age Estimates". Pediatrics. 133 (5): 844–853. doi:10.1542/peds.2013-3285. ISSN   0031-4005. PMID   24777216. S2CID   5895957.