Synonyms: light-for-date babies
Small for gestational age (SGA) babies are those weighing ≤2500 g if born at term. They fall into two groups:
- Babies whose growth at all gestational ages has been low. They are light-for-dates, but otherwise healthy.
- Growth is normal in the early part of pregnancy, but slows in utero by at least two measurements, normally ultrasound. This is due to intrauterine growth restriction (IUGR). They have a wasted appearance with little subcutaneous fat. They are at greater risk of dying.
The very low birth weight (VLBW) baby weighs ≤1500 g.
Significance of SGA
SGA fetuses are at greater risk of:
- Intrapartum hypoxia.
- Neonatal complications.
- Impaired neurodevelopment.
- Possibly type 2 (non-insulin-dependent) diabetes and hypertension in adult life.
The majority of term SGA infants have no immediate appreciable morbidity or mortality.
Approximately 9% of neonates are of low birth weight - ie less than 2,500 g. Of these, approximately 25% are preterm and 85% are small for gestational age.
- Maternal age ≤17 years or ≥35 years.
- Socio-economic class IV or V.
- Weight before pregnancy ≤50 kg or ≥75 kg.
- Smoking - although quitting before 15 weeks of gestation may negate risk.
- Excessive consumption of alcohol.
- Drug/substance abuse.
- Previous low birth weight baby.
- Anaemia in pregnancy.
- Chronic hypertensive disease.
- Maternal polycystic ovarian syndrome.
- Antepartum haemorrhage.
- Multiple pregnancy.
- Congenital fetal defects.
- Intrauterine infection.
There is a variety of methods used to detect SGA fetuses:
- Abdominal palpation (the least accurate).
- Measurement of symphyseal fundal height.
- Ultrasound - estimated fetal weight.
- Ultrasound - biophysical profiling.
- Ultrasound - Doppler flow velocimetry.
However, the following should not be forgotten:
- Most investigations use a one-off measurement (size) to predict SGA, while there is evidence that it is the trend (growth) that is of more value in predicting poor fetal outcome.
- All require an accurate estimation of gestation as a prerequisite for accuracy.
- Most tests diagnose SGA fetuses, rather than growth-restricted fetuses.
- Little allowance is made for important prognostic factors for SGA, such as maternal height, weight, ethnicity, parity and fetal gender.
- If an SGA fetus is found, there should be a careful ultrasound survey for chromosome defects. Karyotyping may be offered.
- The fetus should be monitored with umbilical artery Doppler. A study comparing fetal heart rate monitoring, biophysical profile and umbilical artery Doppler found that only umbilical artery Doppler had value in predicting poor perinatal outcomes in SGA fetuses. Absent or reversed end diastolic flow is associated with increased perinatal mortality and morbidity.
- Timing delivery is a balance between Doppler findings and gestation. If the fetus is less than 36 weeks of gestation, the mother should receive corticosteroids.
- The fetus should be delivered in a unit with neonatal expertise and facilities.
- Continuous electronic fetal monitoring should be offered.
- There is currently no evidence to support immediate delivery.
Care should either be provided for in a nursery at a temperature greater than 24°C or, for very small babies, in an incubator at a temperature of 26-32°C and humidity 65-75%.
Temperature is decided by monitoring the infant's core temperature and adjusting accordingly.
Oxygen is supplied either by a head box or into the incubator:
- The level is adjusted according to monitoring by transcutaneous oxygen electrode or pulse oximetry.
- A level is maintained that avoids hypoxia, but also considers the problem of toxicity on the retina (retinopathy of prematurity (ROP)).
Infection control is important:
- Careful attention should be paid to avoiding overcrowding and the possibility of medical attendants or relatives introducing infection into the nursery.
- Hands must be washed before handling a baby.
Feeding should start six hours after birth, using breast milk as soon as possible:
- Normally, the baby is fed by nasogastric tube or spoon.
- They are put to the breast as soon as they are suckling strongly.
- If the baby is unable to accept enteral feeding then supplemental parenteral nutrition may be needed.
- Regularly check for hypoglycaemia and treat with IV glucose if necessary.
Supplements of vitamin A, C, D, niacin and riboflavin are also given.
If Ca2+ <2 mmol/L, give calcium gluconate IV slowly.
Cranial ultrasound (to detect haemorrhage).
- Spontaneous preterm delivery.
- Respiratory distress syndrome.
- Cyanotic attacks - caused either by inadequate ventilation or cerebral damage.
- Hypoglycaemia - affects 15% of cases.
- Hypocalcaemia - usually occurs in the first 24 hours of life.
- Intracranial haemorrhage - mainly occurs in babies weighing <1500 g.
- Retinopathy of prematurity and sequelae.
- Cerebral palsy.
- Mortality increases with decreasing weight.
- Preterm, low birth weight infants have an extremely high risk of mortality in their first year and parents should be counselled regarding this risk.
Very low birth weight (VLBW) females catch up in growth by 20 years of age, whereas VLBW males remain significantly shorter and lighter than controls.
See separate article Premature Babies and their Problems.
Further reading & references
- Ross MG et al; Fetal Growth Restriction, Medscape, Feb 2011
- Barker DJ; The long-term outcome of retarded fetal growth. Clin Obstet Gynecol. 1997 Dec;40(4):853-63.
- Marchant T, Willey B, Katz J, et al; Neonatal mortality risk associated with preterm birth in East Africa, adjusted by weight for gestational age: individual participant level meta-analysis. PLoS Med. 2012;9(8):e1001292. doi: 10.1371/journal.pmed.1001292. Epub 2012 Aug 14.
- Saving Mothers' Lives. Reviewing maternal deaths to make motherhood safer: 2006-2008; Centre for Maternal and Child Enquiries (CMACE), BJOG. Mar 2011
- Campbell MK, Cartier S, Xie B, et al; Determinants of small for gestational age birth at term. Paediatr Perinat Epidemiol. 2012 Nov;26(6):525-33. doi: 10.1111/j.1365-3016.2012.01319.x. Epub 2012 Aug 29.
- Carter S, Percival T, Paterson J, et al; Maternal smoking: risks related to maternal asthma and reduced birth weight in a Pacific Island birth cohort in New Zealand. N Z Med J. 2006 Jul 21;119(1238):U2081.
- McCowan LM, Dekker GA, Chan E, Stewart A, Chappell LC, Hunter M, Moss-Morris R, North RA; SCOPE consortium. Spontaneous preterm birth and small for gestational age infants in women who stop smoking early in pregnancy: prospective cohort study. BMJ. 2009.
- Zetterstrom K, Lindeberg SN, Haglund B, et al; Chronic hypertension as a risk factor for offspring to be born small for gestational age. Acta Obstet Gynecol Scand. 2006;85(9):1046-50.
- Homburg R; Pregnancy complications in PCOS. Best Pract Res Clin Endocrinol Metab. 2006 Jun;20(2):281-92.
- The Investigation and Management of the Small-for-Gestational-Age Fetus, Royal College of Obstretricians and Gynaecologists (2002)
- Chang TC, Robson SC, Spencer JA, et al; Identification of fetal growth retardation: comparison of Doppler waveform indices and serial ultrasound measurements of abdominal circumference and fetal weight. Obstet Gynecol. 1993 Aug;82(2):230-6.
- Schwarze A, Gembruch U, Krapp M, et al; Qualitative venous Doppler flow waveform analysis in preterm intrauterine growth-restricted fetuses with ARED flow in the umbilical artery--correlation with short-term outcome. Ultrasound Obstet Gynecol. 2005 Jun;25(6):573-9.
- Intrapartum care, NICE Clinical Guideline (2007)
- Walker DM, Marlow N, Upstone L, et al; The Growth Restriction Intervention Trial: long-term outcomes in a randomized trial of timing of delivery in fetal growth restriction. Am J Obstet Gynecol. 2011 Jan;204(1):34.e1-9. doi: 10.1016/j.ajog.2010.09.019. Epub 2010 Nov 5.
- Haque KN, Hayes AM, Ahmed Z, et al; Caesarean or vaginal delivery for preterm very-low-birth weight (< or="1,250" g)="" infant:="" experience="" from="" a="" district="" general="" hospital="" in="" uk.="" arch="" gynecol="" obstet.="" 2008="" mar;277(3):207-12.="" epub="" 2007="" aug="">
- Guideline for the screening and treatment of retinopathy of prematurity, Royal College of Ophthalmologists (2008)
- Morken NH, Kallen K, Jacobsson B; Fetal growth and onset of delivery: a nationwide population-based study of preterm infants. Am J Obstet Gynecol. 2006 Jul;195(1):154-61.
- Mittendorf R, Pryde PG; Magnesium sulfate for the prevention of cerebral palsy. N Engl J Med. 2009 Jan 8;360(2):189-90; author reply 190.
- Kristensen S, Salihu HM, Keith LG, et al; SGA subtypes and mortality risk among singleton births. Early Hum Dev. 2006 Jul 11.
- Hack M, Schluchter M, Cartar L, et al; Growth of very low birth weight infants to age 20 years. Pediatrics. 2003 Jul;112(1 Pt 1):e30-8.
|Original Author: Dr Hayley Willacy||Current Version: Dr Hayley Willacy||Peer Reviewer: Dr Colin Tidy|
|Last Checked: 11/01/2013||Document ID: 943 Version: 25||© EMIS|
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